I think you should clean the throttle body. The IAC valve is trying to compensate for the carbon-encrusted orifice.
Seriously, that'* where I'd start if it runs fine otherwise. Get a $5 can of throttle body cleaner, and look around for a procedure. It'* very easy, though.
Totally unrelated, but start your car and pop your hood. From a position (sort of standing) where you can see the grey engine cover, with your foot on the brake (!), put the car in drive. Does that cover move quite a bit? The front trans mount is on its way out. We just bought an '05 with 54k on it, and it'* already gone. Fix that before it damages the remaining mounts.