Why does my PC restart itself a few seconds after start playing video games?

You can try a rollback to before there was a problem. System restore in windows, Time Machine in Mac

Most likely, a PC shutting down like this could be caused either by Power issue or overheating of Graphic card.Check some other cause for Random reboots

@drhat77 Gonna try that.
@Smitha There is a high chance that my power supply is want to get retire since it’s in my computer more than 5 years. Hope it’s not the case since I have a tight budget this month :(

This was happening to my mom a few days ago. Anything video related would have it shutdown after a few minutes. No warning, it would just instantly cut power. Luckily the fix was some compressed air and a toothbrush. Pics here

An extremely similar problem happened to me not long ago, computer would crash and restart after ~30–45 minutes after starting a game with high graphics, and started getting worse as you describe, eventually doing it on games I knew should not be a problem, like cave story. It did end up being my power supply :-/ (it was quite old, ~7 years). I swapped it out for a nice 750W corsair and I haven’t had any problems since. Sorry I can’t give you a cheaper answer but that seems highly likely.

Admittedly, the cleaning idea should be your first try, make sure your graphics card is clean. But if that doesn’t help I would suggest you start saving. Also, I would very much doubt it’s a software issue, as it’s happening in many different settings. May be worth a try, but I wouldn’t count on it.

A cheap check to determine the cause: Take the cover off and see how much dust is stopping the flow of air in/around the CPU. My PC has an alum. heat sink that will attract dust and block the cooling air.
Use only compressed air [ can or air tank ] to clean out the dust. Use no vacuums!

As other said, its probably overheating, Get as much dust as you can out of there, and hopefully it should rectify itself.
Just remember to disconnect the power first :)

I just want to make sure everyone heard what dgee said. Never use a vacuum inside your computer. A can of compressed air is available at walmart for 6 bucks and will last you twenty cleanings.

A vacuum will fuck your computer pretty fast.

what happens when you use vacuums in your pc? ( i did it once to clean out cobwebs.)

A vacuum can build up a lot of static electricity that can fry the innards. It is like when installing RAM you should wear a grounded wrist strap. It only takes a tiny shock to damage things.

Your motherboard is dying

@ISmart Sorry, but I already figure it out. My CPU is overheat, so to protect itself, my computer restart. Especially when I choose high performance in power plans. I need to buy an aftermarket cooling system.