Question My whole pc keeps Freezing or restarting when i try to play games

[l8n555]

Yesterday i installed a new cpu and motherboard I5 3470 and a Gigabyte GA-H77M-D3H. I tried to play some games but every time i try. i can play for a few minutes then the PC will freeze then after 30 minutes it will restart or instead of freezing it will restart straight away. When it freezes my keyboard and mouse lose power.
I have done a bios update and reset my pc, uninstalled and reinstalled my graphics driver. I am not really sure what to do now, any help would be appreciated

 

[rgd1101]

make and model of the psu?
fresh os install?
check the cpu/gpu temp during the game?