Computer randomly restarts or shuts off? The usual causes

A computer that restarts itself, or just goes dark in the middle of something, is maddening because it never happens when you are ready for it. The good news is that the pattern, when it happens and how it dies, points at the cause more reliably than any error message. Here is how to read it, what to try, and what we test when it comes in.

Three different ways to die

• Shuts off cold, no warning, like someone pulled the plug: heat or power. The computer protected itself, or lost power.
• Restarts after a blue screen: Windows hit something it could not get past. Photograph the code; our blue screen guide tells you what it means.
• Restarts with no blue screen at all: often still a crash, but Windows is set to restart instantly so you never see the screen. Turn that off (search Start for “advanced system settings”, then under Startup and Recovery untick “Automatically restart”). The next crash will stay on screen and tell you something.

Heat

The most common cause on laptops, and on gaming desktops. The fan roars, the case gets hot, and the computer shuts off during a game, a video call, or anything that works it hard, then refuses to start for a minute until it cools. Dust in the cooler and thermal paste that dried out years ago are the usual reasons. Our overheating guide covers the signs and what the fix involves.

Power

• On a desktop, the power supply is the first suspect for cold shut-offs. A tired one delivers enough for the desktop to idle and not enough under load, so it dies exactly when you ask the most of it. It may also take two tries to start, or buzz. A failing power supply can take other parts with it, so it is worth finding early.
• On a laptop, a charger that cannot keep up, a worn charging port, or a battery that can no longer hold the line will drop the machine the moment the load rises. Our charging guide shows how to tell those three apart.
• The wall itself: an overloaded power strip, a loose outlet, or a space heater on the same circuit. Try a different outlet before you blame the computer.

Memory

A bad stick of memory causes restarts at random, doing nothing in particular, often with blue screens whose codes change every time. Windows Memory Diagnostic (search for it in the Start menu) will restart the computer and test it. Errors there are a clear answer, and memory is usually on our shelf.

The other suspects

• Windows Update. If it restarts overnight, or once right after you see “updates pending”, that is scheduled, not a fault. Check Windows Update history.
• A driver or program that started it all. If the restarts began the day you installed something, undo that first.
• An accessory. A failing USB device, dock, or external drive can reset a computer. Unplug everything but the keyboard and mouse for a day.
• The drive. A failing drive more often freezes than restarts, but it can do both. Clicking or very slow file opening points there, and your files come first.
• The board. A failing motherboard can do all of the above. It is the least common and the one we make sure of before suggesting it.

What to try before bringing it in

• Note when it happens: under load, at idle, at the same minute every day, only when warm, only when plugged in.
• Turn off automatic restart so you can see the crash screen, as described above.
• Try a different outlet, without the power strip.
• Unplug every accessory and see if it holds for a day.
• Run Windows Memory Diagnostic.
• Clear the vents with compressed air, with the computer off. Do not open a laptop for this unless you have before.
• Back up your files. A restarting computer is not usually losing data, but it is the right moment to make sure.

What we check

For the flat $60 we read the logs Windows keeps of every crash and shutdown, run the computer under load with temperatures watched, test the power supply, the memory and the drive, and tell you plainly which one it is. Power supplies and memory are usually on the shelf (see parts in stock), so a desktop with either problem is often fixed the same day. A cooling problem gets a cleaning and fresh thermal paste, tested under load before it goes back. The $60 comes off the repair, with a 30-day warranty on parts and labor. It is everyday work in our computer repair.

When to bring it in

When the outlet, the accessories and the memory test did not settle it, when it is getting more frequent, or right away if it shuts off hot or the drive is making noise. Bring the charger. Walk in Monday through Thursday, 9:00 to 5:30, or Friday by appointment, at 746 S Arnold St Suite 3, the black door with our logo on it, straight ahead when you pull in, up the steps. Or book a drop-off online. For a desktop you would rather not carry, pickup and return starts at $39 plus the diagnostic, priced by distance, exact price before you book. Every price we charge is on our prices page.