2000 Saturn SL1 Engine Sputters in Idle

Shakes or Wobbles problem
2000 Saturn SL1 135000 miles

I need advice on two issues with my car:

1) In Idle (not moving) or in Park, the engine sputters. It does not lose power, it just sputters. Sometimes, when stopped at lights, the car lurches forward a little bit. What could be causing this?

2) This might be related to #1. After driving more for about an hour on the hi-way, when I place the car in Park, the RPM's jump up and stay around 2000-4000. They don't drop until I turn the car off and turn it back on. What could be causing this?

Please help
Thank you
AJ