Slow Moving Sun Roof

I have a factory sunroof which I use all the time (day and night - I love the size and the open feeling you get). Recently, as I hit the switch to close it - the motor seem to slow to a stop - at time I need to help push it close. This does not happen every time I operate the sun roof. Have any of you experience this and is it just a motor thing that the dealer can replace? Just want some input prior to me hitting the dealer.

Thanks

"It's what you learn, after you know it all, that counts - John Wooden