mb w124 300e window wont work sometimes what could it be?

Sounds like a loose connection or the switch is going out.

Sounds like you must access the parts inside to effect repairs, since you may need regulator, motor or both. consider the age of your parts and the plastic parts between the regulator and the track grooves. If it is a mercedes and worth fixing, you can have the best repair by replacing all the higher percentage failure items all at once. get the electrical and mechanical corrected at the same time and remove the panel as few times as possible. Your switches in the console can be done as a separate repair and be fixed or eliminated by testing first. When you find the parts you want, and are ready to install, do it all at once and be done with it. or hire it done. I see videos from mercedes source that help and peach parts has informational tutorials with pics to help familiarize you before you start trying to get it apart. Benzworld has many knowlegeable folks answering everyday. and Benz parts wholesale has knowlegeable men you can talk to when buying your parts as well.

thanks for the advice! but i already find my quick sollution,i bought a pack of aspirin and a pack of beer....presto! my headache is gone! oh im just kidding! maybe i should find wiring diagrams might help,by the way thanks!

Mercedes diagrams can be looked up or sent for by the public library. Mercedes quirks can be looked up in the benz bible for your year. switches with beer spilled in them can be rinsed out with brakleen, hahaha, merry christmas.