Someone recently asked me "when did turning computers off and on again to fix problems start?" A colleague, Bob Doran, considered this and replied: "My guess is that it was not done during the valve computer era because turning off then on would almost guarantee a valve would die. With large computers, too, I am sure that turning the machine off would be avoided because the "cold start" was a long process. Reboot the computer, definitely. The reason that it works is that the problem is likely memory corruption and off/on clears all writable memory. So that means its from the 70s with PCs and DRAM memories. Mind you, I think that the technique was also applied to other devices."
from The Universal Machine http://universal-machine.blogspot.com/