I have an '04 C240 4Matic that I recently bought used with 55k miles on it.

It was running great when purchased and then, since I don't know how to drive a manual transmission, I practiced by using the autoshift selector. I don't believe I can do any real damage using that, but now, when in "D", the car has trouble shifting from either 1st to 2nd or 2nd to 3rd (could be 3rd to 4th, but I don't think so because it occurs at lower speeds). It jerks somewhat as it's making that shift, but it eventually makes it into the next gear.

Also, there is a downshift to a particular gear when the car seems to rumble as if the car is driving over a rumble strip but it's not.

I would assume that the car is having trouble shifting in and out of a particular gear but I tried using the autoshift selector and none of the gears seem to have that "transition" problem...although I only tried it once since that seems to be the thing that caused this whole situation and I want to stay away from it as much as possible!
Thank you for viewing!

 

I've driven it some more and the jerking occurs at higher speeds within 2nd gear--not the shift transition from 1st.

The repair person said I needed a new Control Module. This seems like a trustworthy shop and manager but I have searched for information related to replacing a Control Module and couldn't find any.
Perhaps anyone has any experience with this? Doesn't seem like something that would match my expectations for a premium auto brand.

 

I took the car to an independent garage and they felt that the problem was mechanical--possibly the torque converter. But they didn't rule out the Control Module. Hmmm....the saga continues!