It depends.... The warm up phase can be different from day to day. Somedays when its colder, it will idle at a higher RPM during warm up, and then other days it wont have to. My Q, on really cold days, will go up to about 1200RPM, and then drop back down to 500. Now, it goes to 1000 during warmup, and then goes back down to 500.
I cant really tell you what is happening, but it may be time to take it in (or if you have a service manual) and tune it up.
Things I would do to get a better idle:
clean TB intake hose
I cant remember if these cars have MAFS or not, but if they do you can spray some brake cleaner on them (use brake cleaner because it will not leave residue)
There is a sensor type thing that controls the idle (dont know the specific name) that may need to be checked on
I would not take this to a dealer to be done, because most of the stuff done you can do at home with little or no experience.