I agree with riverbend on the fuel pressure regulator (FPR). Especially if the rough running clears up after half a minute to a minute, or so.

The FPR on my 1992 245 steadily deteriorated to the point where it would start perfectly fine every time. It wasn't until a month or three ago that the cold start was followed by rough running just seconds after the start, and it would clear up after about half a minute. The exhaust gases looked and smelled like an overly rich mixture while running rough.

The usual DIY checks on the FPR (smelling the vacuum side and checking the returned volume with a hose in a bucket) didn't reveal anything. Only very very occasionally, the OBD would throw a fuel mix error code during driving.

After some thinking and looking at how the ECU decides what the best fuel mix is (cold and warm), I decided the FPR was the most likely candidate for my problems, and it indeed turned out to be the culprit.

Hope this info may help. Even without the usual signs, the FPR may not be operating correctly anymore.