The wife's 06 'Stang windows do the same, go down about the 1/2 inch when you open the doors and then roll up when you close the door. At first it was a bit unnerving until I got used to them moving on their own. I had a 96 Monte Carlo and I wish it had that arrangement as I did have a few issues with the windows sealing properly at times when entering the car, especially on cold days.