Why Does My PC Keep Restarting?
Causes & Fixes
A computer that keeps restarting on its own is one of the more frustrating problems you can run into — partly because there are so many possible causes. It could be overheating, a bad stick of RAM, a failing power supply, a driver conflict, Windows Update forcing a reboot when you weren't looking, or half a dozen other things. In over 30 years of fixing computers, I've seen all of them. The trick is narrowing it down, and this guide will help you do that. We'll start with the most common causes and work through them one by one until you find yours.
1 First: What Kind of Restart Are You Getting?
Before you start troubleshooting, it helps to know what type of restart you're dealing with. The answer points you in very different directions:
Blue screen, then restart: You see a brief blue screen with an error message (or the sad face emoji — some techs call this "the blue screen of sadness") and then the computer reboots automatically. This is a system crash — usually caused by a driver, corrupted system file, or hardware problem. See our Blue Screen of Death guide for specific error codes.
Instant restart with no warning: The screen goes black and the computer reboots with no error message at all — like someone pulled the plug and plugged it back in. This is almost always a hardware issue: overheating, power supply failure, or faulty RAM.
Restart during or after Windows Update: Your computer reboots itself while you're in the middle of something, and when it comes back you see "Updates were installed." This is Windows deciding it's time to restart for an update — annoying, but not a malfunction. Section 8 covers how to stop this.
Restart loop — never reaches the desktop: The computer starts to boot, gets part way through, then restarts and tries again. Over and over. This is a boot loop and usually points to a corrupted Windows installation, a bad update, or a failing drive.
2 Stop Windows from Auto-Restarting on Errors
By default, Windows is configured to automatically restart when it hits a critical error. The problem with this is that the blue screen of sadness with the actual error message flashes by so fast sometimes you can't read it. Turning off automatic restart lets the error screen stay on screen so you can see what's actually going wrong.
1. Right-click the Start button and choose System.
2. Click Advanced system settings (on the right side).
3. Under Startup and Recovery, click Settings.
4. Uncheck "Automatically restart" under System failure.
5. Click OK.
Now, the next time a crash happens, the blue screen will stay on screen until you manually restart. Write down or photograph the stop code at the bottom — it tells you exactly what went wrong.
3 Overheating — The Most Common Cause
If your PC shuts down or restarts during heavy use — gaming, video editing, or even just running a lot of browser tabs on a hot day — overheating is the most likely cause. Your CPU and GPU have built-in thermal protection that forces a shutdown when temperatures get dangerously high. This is actually your computer protecting itself from permanent damage.
Check your GPU temperature: Open Task Manager (Ctrl + Shift + Esc), click the Performance tab, then click GPU. The temperature is shown there. Anything consistently above 85–90°C under load is a concern.
Check your CPU temperature: Unfortunately, Windows doesn't show CPU temps in Task Manager. You can check in your BIOS (restart and press F2 or Delete during boot), or use a free tool like HWMonitor. A CPU running consistently above 90°C is likely throttling and may be triggering shutdowns.
Common fixes:
— Clean the dust out. Dust buildup on fans and heatsinks is the #1 cause of overheating. A can of compressed air works great for this — see our Compressed Air guide for how to do it safely.
— Make sure all fans are spinning. Open the case (desktop) or listen for the fan (laptop). A dead fan means no cooling.
— Improve airflow. Don't keep your desktop in an enclosed cabinet. Don't use your laptop on a bed or pillow — the vents need room to breathe.
— Replace thermal paste. On older machines (5+ years), the thermal paste between the CPU and its heatsink dries out and stops conducting heat effectively. Replacing it is a simple job and can drop temperatures by 10–20°C. For more detail, see our overheating guide.
4 Faulty RAM
Bad RAM is one of the sneakiest causes of random restarts because the symptoms are inconsistent. Your computer might run fine for hours, then suddenly restart without warning. Or it might crash only when you're doing something memory-intensive. There's usually no blue screen — just a sudden reboot.
Run Windows Memory Diagnostic: Press the Windows key, type "Windows Memory Diagnostic" and open it. Choose "Restart now and check for problems." Your PC will restart and run a memory test before Windows loads. This takes 10–20 minutes.
When it finishes, Windows will restart normally. Check the results by pressing Windows + R, typing eventvwr, and navigating to Windows Logs → System. Look for an entry from MemoryDiagnostics-Results.
If errors are found: You have a bad RAM stick. If you have two sticks, try removing one at a time and testing with each individually to identify which one is faulty. Replace the bad stick. For help figuring out what RAM your computer takes, see our Do I Need More RAM? guide.
5 Power Supply Problems (Desktops)
If you're on a desktop and your computer restarts with absolutely no warning — no blue screen, no error, just an instant reboot — the power supply (PSU) is a prime suspect. A failing or underpowered PSU can't deliver stable voltage to your components, and when the load spikes (like when you launch a game or your GPU ramps up), the power dips and the computer restarts.
Signs your PSU might be the problem:
— Restarts happen during high-load activities (gaming, rendering, stress tests).
— You hear clicking or buzzing from inside the case (the PSU fan or internal components).
— The computer sometimes doesn't turn on at all on the first press.
— You recently added a new graphics card or other power-hungry component.
What to do: Testing a PSU properly requires a multimeter or a dedicated PSU tester, which is more of a technician's job. If you suspect the PSU, the most practical approach for a home user is to try swapping in a known-good PSU (if you have one available) and see if the problem stops. If you're building or upgrading, make sure your PSU wattage is sufficient for your components — online PSU calculators can help you figure out what you need.
Important: If your PSU is modular, never mix and match cables between different PSU brands or models. Modular cables aren't standardized between manufacturers — even matching connectors can carry different pin-outs, and using the wrong cable can fry your components.
If your laptop restarts when it's not plugged in, the battery may be dying and unable to deliver consistent power. Try running the laptop plugged in only — if the restarts stop, the battery is the issue. If it restarts even while plugged in, the problem is elsewhere.
6 Driver Conflicts
A bad or outdated driver — especially a graphics driver — is one of the most common software causes of random restarts. The driver crashes, Windows hits a critical error, and the system restarts. You might see a brief blue screen, or the restart might happen so fast you don't see anything.
1. Update your graphics driver — go to nvidia.com, amd.com, or intel.com and download the latest driver for your card. Don't rely on Windows Update for graphics drivers — the manufacturer's version is almost always newer.
2. Check for recently updated drivers: If the restarts started after a recent update, a new driver might be the cause. Open Device Manager (right-click Start → Device Manager), expand the device categories, and look for any with a yellow exclamation mark. Right-click the device, choose Properties → Driver → Roll Back Driver if the option is available.
3. Check Event Viewer for clues: Press Windows + R, type eventvwr, and go to Windows Logs → System. Look for Critical or Error events around the time of the last restart. The source and description often name the exact driver or component that caused the crash.
7 Corrupted System Files
Corrupted Windows system files can cause all sorts of instability, including random restarts. This can happen after a bad update, a sudden power loss during a write operation, or even from malware damage. Fortunately, Windows has built-in tools to check and repair these files.
Open Command Prompt as Administrator and run these two commands in order:
DISM /Online /Cleanup-Image /RestoreHealth
Let this finish (10–20 minutes). Then:
sfc /scannow
SFC checks every protected system file and replaces any that are damaged. When both are done, restart your computer. If corrupted files were causing the restarts, this should fix it. For a deeper walkthrough of these tools, see our Windows Update Errors guide (Section 4).
8 Windows Update Forced Restarts
If your "random" restart is actually Windows rebooting itself to install updates — you'll come back to find a "Your PC was updated" message — this isn't a malfunction, it's a feature. A very annoying feature. Windows schedules restarts outside your "active hours," but if those hours are set wrong (or set to "Automatic"), it may restart while you're still working.
1. Set your active hours manually: Go to Settings → Windows Update → Advanced options → Active hours. Switch from Automatically to Manually and set the widest window you can — Windows allows up to 18 hours. I set mine from 6 AM to midnight.
2. Turn on restart notifications: In the same Advanced options menu, enable "Notify me when a restart is required to finish updating." This is off by default, but with it on, Windows will warn you before rebooting instead of just doing it.
3. Pause updates when you need to: Go to Settings → Windows Update and click Pause updates for up to 5 weeks. Useful during busy stretches when you can't afford a surprise reboot.
9 Malware
Some types of malware — especially cryptominers and trojans — can cause system instability and restarts. Cryptominers push your CPU and GPU to 100% usage, which causes overheating and crashes. Other malware can corrupt system files or conflict with drivers, leading to the same result.
Run a full scan with Windows Security — go to Virus & threat protection → Scan options → Full scan. Then follow up with a scan using Malwarebytes Free for a second opinion. If you find anything, see our How to Remove Malware guide for the full cleanup process.
Quick check: Open Task Manager and look at the CPU column. If something you don't recognize is using 50–100% of your CPU constantly, that's suspicious. Search for the process name online before killing it — but if it's clearly malware, you know what to do.
10 When to Bring It In
Most of the fixes above can be done at home, but some restart problems point to deeper hardware issues that are hard to diagnose without professional tools — intermittent motherboard failures, failing capacitors, unstable voltage regulation, or a dying hard drive that corrupts data during writes. If you've worked through this guide and the restarts keep happening, it's probably time for hands-on diagnosis.
The restarts are completely random — no pattern, no trigger, no consistent error code. This usually points to an intermittent hardware fault that requires testing individual components.
You're getting different blue screen codes every time. Multiple different stop codes suggest either bad RAM, a failing motherboard, or a dying drive — all of which benefit from hands-on testing.
The computer restarts even in Safe Mode. Safe Mode strips Windows down to the essentials. If it still restarts in Safe Mode, the problem is almost certainly hardware, not software.
You smell something burning or notice a bulging capacitor. Stop using the computer immediately. This is a hardware failure that could damage other components if you keep running it.
Can't Pin Down the Problem?
Random restarts are some of the trickiest issues to diagnose because the cause isn't always obvious. If you're in the Nanaimo, BC area, BigMike Computer Services can run hardware diagnostics, test your RAM, power supply, and thermals, and get to the bottom of it.
Over 30 years of fixing computers — and "it keeps restarting" is one of the most common things I hear when someone walks through the door.
Visit BigMike Computer Services →— BigMike | Computer Repair Technician, Nanaimo BC
📧 BigMikeNanaimo@gmail.com