Random restarts usually mean a hardware problem, a driver conflict, or Windows trying to install updates

A PC that restarts without warning is almost always responding to something specific — not a random glitch. The restart happens because Windows detected a critical error, your power supply is failing, a component is overheating, a driver crashed, or a Windows update finished downloading and forced a restart. Your job is to narrow down which one by checking a few places before the next restart happens.

The fastest way to find the cause is to look at the Windows Event Viewer, which records every crash and restart with a timestamp and error code. You can also check your BIOS temperature readings, review which drivers updated recently, and see whether Windows has a pending restart waiting. Most restarts are fixable once you know what triggered them.

Key Takeaways

  • Windows Event Viewer shows the exact error code and time of each restart, which narrows the cause from dozens of possibilities to one or two.
  • Overheating is the most common hardware cause — check your CPU and GPU temperatures in BIOS or a tool like HWiNFO before the next crash.
  • A failing power supply often causes restarts under load (gaming, video editing) because it cannot deliver enough power; a new PSU is the only fix.
  • Recent driver updates, especially graphics drivers, can conflict with your hardware or software and force unexpected restarts.
  • Windows may restart automatically after an update finishes, even if you told it not to — check Settings > System > Recovery to see pending updates.

Check Event Viewer for the restart error code

Event Viewer records every crash, restart, and critical error with a timestamp and error code. Open it by pressing Windows key + R, typing eventvwr.msc, and pressing Enter. Navigate to Windows Logs > System on the left side.

Look for entries marked "Critical" or "Error" near the time your PC restarted. The most common codes are DRIVER_IRQL_NOT_LESS_OR_EQUAL (a driver crashed), KERNEL_SECURITY_CHECK_FAILURE (corrupted system file or driver), and WHEA_UNCORRECTABLE_ERROR (hardware failure, usually CPU or RAM). Write down the error code and the name of any driver or file mentioned — that is your starting point.

If Event Viewer shows no critical errors near the restart time, the restart was likely caused by overheating or power loss, because those do not always log an error before the shutdown happens.

Monitor CPU and GPU temperatures during normal use

Overheating is the single most common cause of random restarts. When your CPU or GPU hits its thermal limit (usually 90–100°C depending on the chip), Windows shuts down when ready to prevent damage. read HWiNFO64 (free, from hwinfo.com) or check temperatures in your BIOS by restarting and pressing Delete, F2, or F12 during startup (the key varies by motherboard).

Run a program that uses your CPU and GPU — gaming, video editing, or the stress test built into HWiNFO — and watch the temperatures climb. If your CPU stays above 80°C or your GPU above 85°C during normal use, you have a cooling problem. Check whether your CPU cooler is seated correctly (reseat it if you are comfortable opening the case), whether your case fans are spinning, and whether dust is blocking your heatsink or radiator. A can of compressed air can often fix dust buildup in minutes.

If temperatures are normal and restarts still happen, move to the next cause.

Test your power supply under load

A failing power supply often causes restarts only when your PC is under heavy load — during gaming, video rendering, or large file transfers — because that is when power demand peaks. If your restarts happen during these activities but not during web browsing or office work, your PSU is the likely culprit.

You can test this by limiting the load: lower your graphics settings in games, close other programs, or reduce the resolution. If the restarts stop or become less frequent, your PSU cannot deliver enough power. A replacement PSU is the only real fix — a failing PSU cannot be repaired and will eventually fail completely. Buy a unit with at least 20 percent more wattage than your current system draws; a power calculator like OuterVision's can estimate your system's needs.

If restarts happen regardless of load, or if your PC restarts even at idle, the problem is not the power supply.

Review recent driver updates and roll back if needed

A driver update — especially for your graphics card, chipset, or network adapter — can conflict with your hardware or other software and cause when ready restarts. Check which drivers updated recently by opening Device Manager (Windows key + X, then Device Manager), right-clicking your graphics card under Display adapters, and selecting Properties > Driver > Driver Details. Note the driver date.

If a restart started happening right after a graphics driver update, you can roll back to the previous version. Right-click the graphics card again, select Properties > Driver > Roll Back Driver. If that option is grayed out, the previous driver is no longer available; in that case, uninstall the current driver completely (check the box to delete the driver software), restart, and Windows will install a generic driver. Then read an older driver version from NVIDIA (for GeForce cards) or AMD (for Radeon cards) and install it manually.

For other devices, the same process applies: find the device in Device Manager, check the driver date, and roll back if an update coincides with your restart problems.

Check for pending Windows updates and restart settings

Windows can force a restart after installing updates, even if you set it not to. Open Settings (Windows key + I), go to System > Recovery, and look for any message about pending updates or a restart. If one is waiting, you can choose to restart now or delay it — but Windows will eventually force the restart if you keep delaying.

To prevent automatic restarts in the future, go to Settings > System > Notifications & actions, scroll down to Advanced, and turn off "Get tips, tricks, and suggestions as you use Windows." Then go to Settings > Update & Security > Windows Update > Change active hours and set your active hours to cover the times you use your PC most. Windows will not force a restart during active hours.

If you see no pending updates and your active hours are set correctly, Windows updates are not the cause.

Run Windows System File Checker and check RAM

Corrupted system files or faulty RAM can cause random restarts with error codes like KERNEL_SECURITY_CHECK_FAILURE. To check system files, open Command Prompt as Administrator (right-click the Start button, select Terminal (Admin) or Command Prompt (Admin)), type sfc /scannow, and press Enter. Let it run to completion — it may take 15 minutes. If it finds and repairs corrupted files, restart your PC and see whether the restarts stop.

To test RAM, restart your PC and press F8 repeatedly during startup to enter the Windows Boot Menu. Select "Troubleshoot" > "Advanced options" > "Startup Settings" > "Restart," then press F3 to run the Windows Memory Diagnostic. Let it run through at least two passes. If it reports errors, one of your RAM sticks is failing and needs replacement.

Frequently Asked Questions

Can a virus cause random restarts?

Yes, but it is rare. Malware usually hides rather than crashes your system. If you suspect malware, run a full scan with Windows Defender (built into Windows) or Malwarebytes (free version available). Check Event Viewer first — if the error code points to a specific driver or file, that is a better lead than assuming malware.

What if Event Viewer shows no errors at all?

A blank Event Viewer usually means the restart was caused by overheating or power loss, because those can shut down the system before Windows logs an error. Check your temperatures and power supply first. If both are normal, the problem may be a loose RAM stick — try reseating both sticks by opening the case, pushing them out, and pushing them back in firmly until they click.

Should I disable automatic restart on system failure?

Only if you want to see the blue screen error code before the restart happens. Go to Settings > System > About > Advanced system settings > Startup and Recovery, uncheck "Automatically restart," and click OK. The next crash will show you the error code on screen instead of restarting. Write it down and search it — that code is often more helpful than Event Viewer.

Does a BIOS update fix random restarts?

Sometimes, if the restart is caused by a chipset or power delivery bug in your current BIOS version. Check your motherboard manufacturer's website (ASUS, MSI, Gigabyte, etc.) for a changelog listing your specific error. Only update BIOS if the changelog mentions a fix for your problem — a bad BIOS update can make things worse.

What if I have tried everything and restarts still happen?

The problem is likely a hardware failure — a failing motherboard, CPU, or power supply. At this point, testing with a different PSU (borrow one from a friend if possible) is your best move. If restarts stop with a different PSU, your power supply is failing. If they continue, the motherboard or CPU is probably the cause, and a repair shop can diagnose further.