strange starting problem

I just bought a used 2004 jeep wrangler 4 cyl engine it started fine for about 2 weeks and now sometimes it just wont start it just makes a clicking sound and othertimes it will start right up. But when it is just making the clicking sound and i slam my door really really hard, it will start up on the next turn. is there somekind if loose connection i should be looking for? Any help would be appreciated.

Sounds like a bad starter motor. If one of the windings is broken it will do that, with a bit of a bump or nudge (slamming the door) it can get over to touch the next winding. If that is what it is then its a new starter motor you need. Only other thing I have seen do that is a rusty connection at the battery, ground at the block, or either connection on the solenoid. It can be tested by using a volt meter at the motor terminal of the solenoid, if it has full voltage when it just klicks then its the motor.

Replace the starter. Easy to do, but you will need the correct tools.