I just had the same problem happen to me last week. For a minute i thought I burnt out the motor because I rolled up the window while driving and did not notice that the switch got stuck in the down position.
I took apart the door and noticed that two of the rubber mounts that the motor sits on are in pieces and no longer even hold the motor. The window did itself did not present any resistance, just the motor.
I dissasembled everything, lubed up all moving parts and the motor, although still extremely hot, rolled the window up without a problem.
I noticed two plastic caps on the motor, sorta like the ones you have on cases of moving parts so you can lube them, but I doubt this is it, but I am wondering what those are for.
Even now that the window is all lubed up it still seems to be having a hard time rolling up. I still have to clean the switch to make sure that it stops sticking, and at the same time have to replace my deck wiring completely.
1985 190E 2.3L - a constant project.