I have the same problem in the front passenger door window in my 87 300e. Dissambled door, cleaned & lubed but no improvement. However, the glass seems to slide up with less restriction when the weather is colder, suggesting contraction of rubber seals is helpful. Hope someone comes up with something.

__________________
87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)