Computers are multiple layers of massive complexity. Somewhere in that complex stack it's very easy for 'something' to go wrong. When it's first turned on the

Computers are multiple layers of massive complexity. Somewhere in that complex stack it's very easy for 'something' to go wrong. When it's first turned on the computer works, so it's clear that there's an initial 'state' where all those layers of complexity are in alignment. Turning it off and on again is the best way to try and replicate that initial successful state.