repo man wrote:It is very possible that you have enough juice in the battery to turn on the lights and some other accessories, but not enough to turn the starter. Have you tested the battery itself?
Exactly. If this happens every time you start the car, it may be alternator related (assuming the case is as repo suggested). Watch the battery light when you drive: does it fade in and out, depending on rpms/load? If it does, it's almost certainly the alternator. (That's all exactly what happened to me every time an alternator's gone out on me.)