Too bad there is no answer to this since I have the same problem with my 85 190E 2.3L.
Only when cold, it hesitates on acceleration, then once it warms up it runs perfectly fine. Weather is getting colder now here (Canada), it was 10C in the morning and the car missed a beat twice, as soon as the temp built up, it was like new.
I have a few options in mind, tune up, although it was done about 15K ago, but the car was sitting for a year in my garage as I restored it, temp sensor, I have a new one, I'll put it on tonight and see if it makes a difference, and possibly the cold start valve.
Cold start valve makes sense since it supplies fuel to the engine when it's cold, but the valve itself might be perfectly fine, it might be a sensor that triggers it, hence the temp sensor. I might rig something up to see if it clicks on or not.
Any other suggestions?
I seriously doubt it's ignition related since I've seen this before, but a tune up never hurts
xp