Why does the system itself reboot (Win 8.1)?

Question

Windows

Good afternoon, forum users. Until today, my PC worked without problems, but after turning on the computer again while playing PES 2014 and Need For Speed ​​Rivals, after a while the system itself began to reboot.
An interesting fact is that if I do not run games, surf the Internet or the like, the computer works perfectly. The video card and the processor are not heated, checked, the operative also checked everything is normal. Rebooted the system, but the problem still persists. Who else can advise instructions on how to fix the problem?

Answer 1

Stop playing toys =)