Computer keeps restarting when i start up a game

my PC keeps restarting every time i start a game it is just fine until then OS runs internet pulls up even the browser games work but once i start up something like D3,Life is strange or any other game i have it restarts withing seconds
GPU: 2 960 GTX MSI 2 GB gaming series
CPU: AMD FX-8320E vishera 8 core
PSU:650 watt corsair
Ram:2 1866 Ripjaw 8 GB sticks
HDD:1 TB Samsung
SSD: 125 GB Samsung (OS Only)
Motherboard: Gigabyte 990FX G1 gaming series

it was working just fine till a few weeks ago i have Replaced the Motherboard,CPU,Ram,HDD,SDD and PSU
if anyone else has any ideas please help