its a couple of things. usually its the whiskers drying out or there are these sponge with micromesh cloth finger that push the bottom of the window out and they dry out and shrink and the window starts to rattle or squeak, it can also be the roof belt line seal.
the best is when you can locate the squeak to the top or bottom of the window. but if the window needs adjustment then you have to take the door panel off and it can be a bit of a nightmare, adjusting and readjusting and you may never get the window to sit just right.
get some silicon oil usually comes in a spray or they make it in liquid form you coat all the rubber where the window touches and usually the squeak goes away. sometimes it takes a couple of layers to make it stop.
sometimes roll down the window and roll it back up with the door closed and then give that last turn a little more force on the crank to push the window into the seal and the stoppers with some more force and it stops the squeak.
What really helps
Sub frame connectors. that stiffens the door frames on the body and keeps the body from wiggling around the door and making the windows squeak.
