The first part sounds like the classic loose battery terminal nut. Have you done any work on it that the cables were off of it or maybe added an accessory?
Even if your answer is no I'd check to see if one of the nuts isn't loose
Edit: Dammit - clicked on reply too soon - I wasn't done...
The not restarting part sounds like it could be a bad battery. I had the same symptoms and took it to an Autozone to have the battery checked. Even though it came out ok it still wouldn't start. I ended up throwing in a Walmart battery and it started perfectly.