eratic rev

I have an 05 stratus sxt sedan 2.4l that upon startup the rpms jump way high and also upon driving and stoping at a light the rpms will jump up and then level out and jump up again? any idea what would cause this? Also when putting it in reverse the car seems to jump back. Any help with this would be apprectiated

Whoh! This is a freaky one. Could either be a computer issue, or some of the parts in the throttle control. Swing by one of those big chain auto parts stores, b/c some of them will hook it up to a diagnostic computer and give you the code that it gives out. And a buck says the idle issue might even be what's causing the hard shift into reverse.