Was starting my usual morning routine, cup of tea, turn on the PC to check things... And the PC wouldn't power on. Checked it a few times, opened it up, ran through the usual suspects. Flick the power switch on back, mouse and keyboard light up, but absolutely no reaction when the main on/off switch was pressed.
Couldn't go in-depth since I had to start work. Then several hours later I walk past, pat the top of the PC pondering on what to check when lunch arrives... And the PC turned itself on.