Why does my pc restart when I play a game?

My pc restarts when I play a game e.g. With csgo, valorant, and fortnite

But if I'm not in a game right now, it usually doesn't restart, maybe it is the bios?

Check your hardware temperatures. If these are too high, the computer can automatically switch off and restart.

The PC restarts because it crashed.
Your system is unstable.

Why?

The temperatures are ok the graphics card gets warm up to 50 degrees

the cpu up to 61