2004 Jeep Cherokee SHIFTING

I have a 2004 Jeep Cherokee and when going form park to drive it jerks the whole car. What could be the cause of this? Also, the other day I put my jeep into reverse from park and it began shaking and I stoped my jeep put it in park and the idle shock then stoped. And last while driving the other day my RPMs went high then low as I accelerated and as I accelerated my car felt like it was jumping forward like it was trying to get gas (but there was plenty of gas) Help