Computer shuts down 30s after I press launch.

Was playing a game earlier today and the computer just randomly shut off. Turned it back on, opened league, then clicked launch, about 30 seconds after no matter what I do, it shuts my computer off. Nothing else is doing this, and is quite irritating. Can someone please assist me in this. Never had a problem over the last 7 months until now. Thank you for your time! update-update. i've also done system recovery, reinstalled 3x, updated drivers, ran malware/ccleaner and done a few restarts. it still persists. please someone help me!!! missing out on my weekend time!