Hi,
Do a search on this forum, there are quite a few Mercedes gearbox manuals and Merc troubleshooting technical docs. I did download them ages ago, but I can't find them, but do a search - they are available on this forum.

 

First thing you should consider is changing tranny oil and filter if this service is forgotten since ages... the proper oil for sure that have m.benz approval... you can accomplish this service perfectly by thinking about differencial oil change which is a simple and cheap work.

 

You didn't list what year you have but check your vacuum tubes for leaks and cracks in the nipples where it connects (and that they are even connected - both to the transmission and the intake manifold or wherever.) Make sure the oil level is correct and not too old, make sure the bowden cable and kick down are set correctly, the modulator could also be the cause.

 

He mentioned the conductor plate issue, he doesn't have any vacuums lines going to the transmission. Indeed it seems like the conductor plate is on its way out. The good news is despite this feeling pretty bad when it happens, your transmission can handle the abuse. Replacing the conductor plate and putting in fresh fluid and filter and everything should go back to normal (or perhaps be even better than normal).