Seems like an overheating issue or hardware. I have the same issue with my
xfx 290x. could also be if you to much power drawn from psu or faulty. I'd
test the video card in another computer and the test the psu in another
computer as well, unless you have a voltage reader. update drivers, undo
overclocking, check ram, rearrange ram, remove all but one ram and test it
how it works, check your cpu to make sure it's seated properly, make sure
fans are all blowing in one direction out of pc, make sure your not
exceeding power capacity of psu. check error log to see what could have
crashed the pc.
There's more to do but that's all I can think of off the top of my head.
Can U share the full specs of your PC to see some possible issues?