Bumping Sound from Under Driver Feet?

Does the noise happen more as you accelerate? I have seen the engine mounts go out in these cars and allow the exhaust to contact the underside of the car to make a bumping noise that is rhythmic. It could be a loose underbody panel or splash shield so I would look under the car to see if anything is hanging down. There is a center support of the driveshaft that can go out and cause this kind of noise it would be at the transmission tunnel. All of these inspection will require the car to be on a lift. Once lest thing is the muffler system hangers might be broken allowing the exhaust system to move around excessively. Please upload a short video in your response of the problem, so I can see what's going on. Ken

This has happened while traveling on the interstate at 65-70 mph. The car has been checked out by Henrick's Mercedes Benz of Durham, NC and two of the best private Mercedes Benz service centers in the area. The car was placed on lifts and test driven. The front wheels were removed by one of the private shops. This does not happen on acceleration. This is not a very loud sound, rather is low. There is nothing hanging out of the ordinary.

Thank you.

I'm have seen the struts cause this noise and it is not obvious by visual inspection. Here is a guide that may help as well.

https://www.2carpros.com/articles/popping-noise/

Please upload a short video in your response of the problem, so I can hear what's going on if you can.

It turns out that the sound is a series of thumps, and it seems to be coming from the steering wheel. It comes in sets of 2 thumps or 3 thumps. It is a very soft sound. It has been suggested that the problem is shock/strut towers or the electric steering rack. Another suggested a valve in the air ride. One shop suggested that there might be a problem with the lane keeping system. This is not affected by accelerating or decelerating. Thank you for your assistance.

I have seen the driveshaft center support go out on these cars, also are there any body codes? Did the shop un the body codes to see if any were present?

Here is the location of the driveline center support, I would grasp the shaft and check for play at the support. Check out the images (below). Please let me know.

Wouldn't the drive shaft make a constant noise or sound. The sound from my car is barely audible and in patterns of 2 or 3 thumps from the vacinity of the steering wheel. Also, it doesn't every day or every time the car is driven. There is no rattle or banging or grinding. There is no code, but the thumps are connected to one of the warnings systems as an alert on other models. The thumps are patterns of 2 or 3 which represents an intended warning signal.

Gotcha, yep this can be the electric steering going bad, I would run a CAN scan to see if any codes are present that point in that direction.

https://www.youtube.com/watch?v=InIlnsjOVFA

Let me know how it goes.

I would check the tie rod ends as well, here is the location of the steering gear. Check out the images below