1. if you jump start doesn't work, then you can eliminate all power related reason (battry, atlernator).
2. if you can hear the sound of trying to start, but can never start it. I think it is very likly to be the timing belt.
Timing belt is responsiable for air opening/closing, fuel injecting, sparking... if the timing belt is not working, the engine will shutdown, and will not start again.
Now is the season that mouse would go into your timing belt and made it skip a beat... or stuck the belt.
