I have a 2005 GTP and when not moving in gear the steering wheel shakes. Doesn't do it when in park. It comes and goes multiple times per drive too, as in at one stoplight it shakes really bad and then the next its barely noticeable. It doesn't seem to be temp related or when the A/C is on or off. What should I look at or do to figure out whats causing it? Maybe take the belt off and see if it still does it to see if its a pulley issue?
EDIT: Is an idle at just below 700 with the A/C on and just below 600 with it off normal? Seems pretty low to me