GTX 560 Faulty?

Hi guys, recently I just finsihed building my new rig and here is my list of specs

Mobo: Asrock extreme 4
CPU: i5-3570k
Heatsink: Coolermaster Hyper 212 Evo
GPU: Asus Gtx 560
Ram: Gskill 1600 8GB (4 gb x 2)
SSD: Samsung 830 128Gb
HDD: WD Blue 1 TB
PSU: Corsair GS600 V2


When I play games my computer it will decide to restart within 5 minutes of playing. So I went forum surfing and read somewhere about stress testing my GPU and I found a program called OCCT. On the default settings of my GTX560 on a stress test it will cause a computer restart within 2 minutes of doing the stress test. So I was convinced it was a GPU fault right? Or is it something esle?

Also when it restarts, there is no BSOD or any notice, it just restarts like if I was to press the restart button on my case.

Any help will be great! Thanks