RE: Getting an entry position Do not drive on my 05 S500
Sounds like a Body CAN issue.
Not easy for the DIY'er to fix. You are talking digital communications. Not a straight sensor / receiver circuit.
Suggest starting point is to get vehicle on SDS Star Diagnostics at MB dealer and determine what if any codes are present. Body codes are on a different "circuit" to engine codes and cannot be read by normally available scan tools.
Can you confirm that the water drain in the Air Con plenum chamber at the back of the engine bay is not blocked. Shine torch to ensure you can't see any water! Common problem is for this to be blocked and not to be spotted at service allowing water to build up and under certain conditions wet "delicate" electrics inside the car. Do you park near pine trees? Has it been wet lately? Do you use a car wash? Does the car have a tendency to fog up?
Everything points to a fascia area CAN issue. Need to determine where the fault lies along the CAN. Tedious, time consuming and really need help from SDS.
Could try disconnecting the battery for a while (ensure you have your radio code!) This reset process might just resolve matters but wouldn't hold your breath. Have you tried moving the steering column using the "manual" movement switch? I assume you have.
I also assume you have checked the multiple fuses and relays in the electronics box in the engine bay that control (especially) the steering column function?
Could be the Instrument Pack since this is on the CAN but these are expensive to swap out without diagnostic evidence.
Hope this helps somewhat. As I say not a DIYer job.