PC restarts and gives black screen when playing most games.

[Questin]

My PC restarts and gives me a black screen whenever I play games. Whats weird is I've been able to play LoL for weeks and it hasnt restarted. I've had it taken to a repair place twice without them being able to fix it. They believe it's a motherboard issue. Any help is appreciated.

PC Specs:
EVGA 600B Bronze 100-B1-0600-KR Power Supply, 600W
EVGA GeForce GTX 960 4GB SSC GAMING ACX 2.0+
MSI Intel Z97 LGA 1150 DDR3 USB 3.1 ATX Motherboard (Z97 PC Mate)
Intel Core i5-4590 BX80646I54590 Processor (6M Cache, 3.3 GHz)

 

[Vic 40]

Did they test with a different psu? First thing that i'm looking at now.