Guys, need help! Computer won't turn off

In general, such a problem, I didn’t start the computer for 2 weeks, before that everything was fine, now while playing gta 5 (it crashes, (it turns off and then reboots).
What could it be? Please advise what to do
Thanks in advance
And by the way here are the characteristics:
Video card: gtx 970 (4 GB)
Proc: i5-3470 (3.2 mhz)
Power supply: (zalman 700 w)
RAM: 16 Gb