my car just did this and i spent about 8 hours total messin with shit, tracin wires, tightening connection and all that fun stuff. i posted my prob on this site and one of the first things i was told to try was the battery. i was stuborn and didnt think it was the battery but eventually i switched it with a good one and it fired right up. and if your battery is testing good for volts it could still be lacking the cranking amps to turn over that starter. so save yourself some time and just put a friends good battery in and test it out. also if its a manual push start it and take off the pos batt cable while its runnin if it quits then its your alternator....i ran into that one too

good luck