Does your MB do this?
So I was cleaning my car yesterday (84 280CE Euro), giving the centre console a good clean when I hit the window button, to my suprise the window came down even though the key was off. Since I can't read my owners manual (it's in German) I didn't know if it had a timer ala Volkswagons.
Anyway later I returned and it still had power to the windows, until I closed the doors, then no power. I guess it's a feature so you can close a window while getting out, but then why not power them all the time?