similar problem here
I had a similar problem with my 85 190E, but, it seems to have fixed itself. I had this happen only after driving in the rain, so my guess is that something got wet, and caused this to happen, probably a short.
Normally when something like this happens, I unplug the O2, of course, this will only have an effect when the car is actually warm, since the O2 does not provide any readings until it warms up, so it is not a part of the equation. However, I once had this problem happen to me on the road and since the O2 plug is within hands reach, I would unplug it and see if there is any difference or not.
This time, when the cold weather kicked in, and after driving in the rain, my car started to hesitate about a minute after a cold start in the morning, it would hesitate, for about two minutes, and then everything went back to normal. It just happened this past week, and just as I was getting ready to take a look at the problem, coming back after school, the problem dissapeared and has not come back since. My guess that this is one of the electrical gremilins or something on its way out, I'll find out soon enough.
1985 190E 2.3L - a constant project.