I have had my system for over a year, its stability over-clocked at 4.3GHz, I have a corsair 1200W PSU and Gigabyte board, its been doing this strange thing for ages where when I turn on the PC it clicks a few times then the RAM beeps, this is fine. Now heres the issue, after shut down if I don't switch the PSU off the system enters a cold boot mode where sometimes it just restarts over and over, or it clears the CMOS and I get an error message saying due to voltage changes blah blah, but its not the voltage changes as it works all the time if I switch the PSU off at the plug but I shouldn't need to do this.

Any Suggestions?