Hey, check your "sub wiring harness" on the Battery to starter.. Make sure everythings tightened up right, also make sure all the connections on the starter are nice and tight.
If everything turns up good, have a friend try to start the car, while you hit the starter with a crow bar, or something like it.. Make sure you give it a "GOOD" couple of hits, while your friend is trying to start it.. If it starts like that, then its your starter.. and sometimes you can perform this procedure, and not have to replace your starter because it unsticks the solenoid/shaft.