Might be two factors can play a role here:
1. Electric contacts (including motor's brushes), switches and connector oxidation. Working contacts are keep clean by the current flowing through.
2. Rubber sticking - both seals and rubber stops being pressed by the glass can stick one to another making the separation force much higher than typical
What to do? Use the car more frequently and try to keep rubber rails clean.
Both phenomenons I experienced for newer cars (e.g. E30), where electric equipment was not fully functional and window rubber seals are sticking to the glass.
Even for one of E91s, I was forced to change plastic holder/bumper (or complete mechanism) of the bowden cable window mechanism few times. The root cause was the same: at the startup static friction was just too high for crunchy plastic but the motor was strong enough to keep it moving.
It had happened to me also two time when I was going on long trip. I was really "happy" as later on window was slipping down while driving.
1. Electric contacts (including motor's brushes), switches and connector oxidation. Working contacts are keep clean by the current flowing through.
2. Rubber sticking - both seals and rubber stops being pressed by the glass can stick one to another making the separation force much higher than typical
What to do? Use the car more frequently and try to keep rubber rails clean.
Both phenomenons I experienced for newer cars (e.g. E30), where electric equipment was not fully functional and window rubber seals are sticking to the glass.
Even for one of E91s, I was forced to change plastic holder/bumper (or complete mechanism) of the bowden cable window mechanism few times. The root cause was the same: at the startup static friction was just too high for crunchy plastic but the motor was strong enough to keep it moving.
It had happened to me also two time when I was going on long trip. I was really "happy" as later on window was slipping down while driving.