Wow, it must be a common problem on these cars. I also have a 1985 380SE and it has a little problem.

When first started, it starts fine, but if it is cold out when you first start it and press the gas a little, when it idles back down- it idles low and goes back up until it warms up. I always let it warm up before taking off, but when I first accelerate on the road, it acts like it wants to stumble, then it clears out and does not do it again. It also always sounds like I have a slight miss (splutter from the exhaust) when idling, but the engine does not shake. Not sure about this. ???

Then, after it is warm and I restart and place in gear- I have that stalling out problem that sometimes occurs. Sometimes too when I am idling at a stoplight, it will have a sporadic stumble, as if it wants to stall. One time I made a quick stop at a light and it stalled when it geared back into first. As far as my idle goes, it seems OK, around 600 when in drive and about 750 in park, but there have been times I noticed it is near 1000 rpms when in park, but not always.

I am wondering if all of this may not be my problem too. I suppose I should take it to one of our local MB shops and have it checked.

Good luck to you!