2003 Dodge Intrepid 2003 Intrepid has intermitent starting

My 2003 intrepid sometimes wont start. I initially thought that maybe the chip in the key was bad but learned that it is magnetic and it shouldnt make a difference. Sometimes driving down the road it will jerk real bad only over a certain amount of rpm's. I can either let of the gas and it stops untill I press it again or I turn the car off and then back on and it usually fixes itself. The starting problem started about six months ago and I can put the key in and it will turn over but not start then all of a sudden it will. Seems like an anti theft problem of some sort. Also the key comes out of the ignition even with the car on? Any help would be great.