This thread is for a different set of symptoms, but it has some basic debugging techniques...
http://www.peachparts.com/shopforum/vintage-mercedes-forum/168614-idle-hunt-2mins-only-when-cold-280se-71-3-5-v8.html
My old 300sel 3.5 would hunt when the electric sensor on the air cleaner was connected. Not that disconnecting it was a good cure, but it was another diagnostic data point.
-CTH