Computers are run by little gnomes and sprites that live inside of it. Occasionally, they'll go on a coffee break and stop working. Or they'll get grumpy from something and start acting up. But after the coffee break's over or they've calmed down a bit, they go back to working just fine.
At least, that's as best as I can explain when things go haywire for no reason, and then fix themselves also for seemingly no reason.