My advice: replace the motherboard (usually means a new CPU and RAM also).
Kees
My desktop Pc that I have had for about 3 years had been switching itself off every now and again for the last couple of months but for the last few days whenever I try to switch my PC on it just restarts/ reboots itself after about 4 seconds over and over again. I have tried putting a different PSU into it, Putting more thermal paste on the CPU, booting up with the hard drives unattached and taking out my RAM sticks one by one. Please advise.

Chowhound
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