Slightly rough running betweeen 75c and 82c
 

Having a slightly annoying problem. On my 98 ML320, as the engine warms up from cold, as the temperature passes through about 75c and on through about 82c, the engine seems to miss a bit.
What could it be?

If you're looking for advise, I would advise taking it to a shop, if it really bothers you.
There were/are so many problems with the 98 ML's, there really isn't one or two common things that would cause this. Or I could tell you to check.
You ask "what could it be?" - any number of things.

Is the problem consistent? Does it miss more or less while accel/decel/ idling??
Try to get some more info and really narrow it down.

The stunbling only occurs as the ML is started from cold, meaning, coolant temperature at 40c or below. The problem manifests itself only between about 75c and 82c. The problem also only manifests itself if I am stopped with my foot on the brake and the car in drive in that temperature range.

If I am driving through that temperature range, there is no problem.

When I leave from the stopped position when rough running, the engine accelerates as it should.

If this were a carburated engine, I'd say the choke was applied too long and it seems as if the engine is running slightly rich in that temperature zone. Is there a temperature sensor that controls fuel enrichement in this narrow band of temperature? Any ideas what it could be?

Seriously, the 98 ML's had/have SO many freaking' driveability problems.
Your best chance is to take it to a good shop.