PSU Issues, Random Reboots, CX500M

Hello, i recent built myself a new PC a couple days ago, issue being that my PC will randomly shut down then boot back up with no warning or notification.



Ive tried troubleshooting the best i can:

Reinstalling Windows - NO EFFECT

Unplugging GPU - EFFECT, When i unplugged the GPU the system did no restart within the 2 hours i had it running, however the reboots are random.



I've had the system running entirely stable for the past 2 days with NO reboots then a couple hours ago it did it!



Im starting to think my PSU is faulty or just not enough? (i've used PSU calcs and they all vary in results)



My Specs; http://ift.tt/1vcfQ7N [The Pentium&280 ARENT OC'd]



Should i buy another PSU? was thinking of the EVGA 750B (To be safe and have headroom)



Someone Help please! ive no clue what to do!

PSU Issues, Random Reboots, CX500M