Welcome to Free PC Help, InFerect.
Does Windows keeps running simultaneously if you are not playing games or the
condition still persists. Try keeping the computer idle for 10 minutes and see if it turns off. I hazard a guess but I think it might be a malware issue. However do
not do anything unless the experts here advise you to do so. Try and see if you can operate the computer normally without rebooting or not? Good Luck.
-- Goku