Have had this problem over the years on my 77 450sl. Always fixed witjout parts replaceent! First look for glass aleignment. If off adjustment,wil wedge shut gong up, overheat switch and shut down. After confirming alignment in channel, also no obstruction, hold window full open, open door and spray wd 40 inside door on control arms and regulater, (wont hurt motor) try switch with door open, in most cases good for a few more years, good luck, Abe G