Computer constantly rebooting. Please help!

[Anonymoose_]

Hi, so I built my PC in the summer of 2014 and all has been working fine until now. My computer has started rebooting for no reason. It will work for 5 or 6 hours then suddenly just shut down and reboot automatically. When it gets past the BIOS and onto the page where it says "Start Windows normally" it will shut down again and reboot. Occasionally it will let me log in but then instantly reboot and other times it won't let me access the BIOS before it reboots usually I'm not quick enough to get to the event viewer before it reboots again. I figured it could be a couple of things; the PSU dying or my chipset is fried. The reason I said that is because lately I've been having random temperature warnings for my SIO over 70 degrees. I'm pretty stumped with this one.
My system:

PSU: Corsair RM 800w
CPU: i7 4770k
Motherboard: DH87RL (crap I know!)
32gb RAM
GTX 980

Thanks for your help!

 

[ksells]

Have you got a spare PSU to test it with? At least then it would narrow down the possibilities, and it would save from buying a new motherboard if that isn't the causd

 

[Anonymoose_]

Have you got a spare PSU to test it with? At least then it would narrow down the possibilities, and it would save from buying a new motherboard if that isn't the causd

No unfortunately I don't