Random restarts

[Nocturnis]

Hello,
For the past months i've encountered random restarts (as in computer simply shuts down without any warning and boots up again). They usually happened after i start the pc and it doesnt seem to matter what i do after i start it (i got restarts happen during gaming, i had restart happening during browsing only or even when i was in UEFI). I get around 3-4 of these restarts then the pc is stable and runs for hours with no problem.

My setup is :
Asrock P67 Extreme 6 MB
Intel I5 2500k
Scythe Mugen 2 CPU Cooler
Sapphire AMD Radeon 6950 2 Gb
16 Gb Corsair Vengean LP 1600 Mhz CL9
Corsari GS 800W
Western Digital Caviar Black 1 TB
Windows 7 Student 64 bit

 

[Z1NONLY]

what are your temps?

 

[SubJectioN]

That's called a hard cycle; as asked above, what are your system temperatures?

Check all your systems cable configuration for any loose fittings especially around the PSU.
When did this first start happening?
Did you installed any updates or insert any external hardware?

Best regards
SubJectioN

 

[Nocturnis]

Well as for start happening it started a few month ago i think when the weather started getting colder.
Temperature wise :
Asrock AXTU reports : 45 C on the CPU and 41 C on the M/B