Windows 11 (or 10) doesn't include an option to schedule an automatic shutdown of your computer, but it's possible to use ...

If Windows 11/10 shuts down instead of restarting when you press the Restart button, check Power button options and settings ...

It is probably the first thing you must do when your PC shuts down automatically while playing games. Suppose you have an aged computer and often run multiple heavy-weight apps simultaneously.