Earlier in the week my computer rebooted itself overnight and when I got to it it was stuck in a loop of powering up for 2 seconds, then rebooting.
I suspected the PSU, and have since replaced it but the problem is still there. I have reseated all psu connections, removed and replaced all ram one by one, isolated the SSD and Dvd Drive, and tried starting without power to the video card, and none of the above appears to have worked.
Interestingly when I attempted a boot with no ram in, it didn't get to the stage where I assumed it would start beeping at me. Not sure if this helps.
My next thoughts are potentially a failed video card? Is there any other options I can try at home without replacing more parts?
EDIT: Also, the initial boot will last maybe 2 seconds, while the reboots only last 1 second or so. Not sure if this helps.