Why do my RPMs get high when I sit for 5 minutes? Please help! :)

What is your question?

Hey. Ok, I drive a 2001 Volkswagen Jetta GLX (the 6-cylinder one). My problem is this, when I am driving relatively slow (25 MPH, in traffic, stopping and going) my RPMs get high. When I start driving again though, they get back to normal. This is the problem that erks me: when I am sitting, in park (air and radio on) my RPMs get up to 1000, but the little bar is shaking up and down. Then, when I put my car into gear, it is like I am pushing the gas, when I am not?! What is this problem, and how can I resolve it...? Thanks! :)