Sabertooth Z77 Troubleshooting help.

Hi have have built my own computer see specs below, recently i have encountered a problem where the system will randomly turn off for no apparent reason with no warning or shutdown screen. The system will then proceed to automatically restart. It then loads up the BIOS screen and sometimes will start windows, however, sometimes it will get suck in a loop where the BIOS screen loads cuts out and reloads the BIOS screen and the only way to stop this is to hold the power button for 5 seconds. I have attempted to fix the problem by doing the usual things clearing CMOS and updating the BIOS. I have also tried booting with out GFX card etc and just had one stick of ram and the cpu and the primary HDD. Just wanted too see if there is anything i can do before going through the hassle of contacting Asus. It is also worth nothing that this is a recent purchase of less than a month. Any help would be greatly appreciated.

Matt

Intel Core i5 3550 3.3GHz Socket 1155 6MB Cache
Asus SABERTOOTH Z77
Be Quiet Pure Power 630W Modular PSU
Kingston Hyper X 8GB 2133MHz DDR3 CL11 DIMM (Kit of 2) XMP Beast Series
EVGA GTX 660 FTW 2GB GDDR5 Dual DVI HDMI DisplayPort PCI-E Graphics Card
Samsung 840 SSD - Basic
Seagate 1TB 3.5" Barracuda SATA-III 6Gb/s Hard Drive - 7200RPM 32MB Cach
Samsung 24x DVD Writer SATA - Retail Box Version

Not sure if necessary but will include anyway
D-Link 200Mbps Powerline Adapter
Corsair Carbide 300R Case with Window