Mercedes CLK Diesel Heavy Steering and Vibration Issue

Oh my goodness, that sounds concerning! I had a similar experience with my old Vauxhall Astra, although the symptoms weren't quite the same. The steering would get stiff at random times, and the electronic stability system light would come on. It turned out to be a faulty angle sensor. Was a real nuisance especially when parking. Did you have any work done recently, like suspension or steering components replaced? Might be related to the sensor needing recalibration.

No recent work done on the suspension or steering. Just started happening out of the blue. If it's a coding issue with the angle sensor, would that explain the increased steering effort and vibration, especially at lower speeds?

Yes, that's very likely. The steering angle sensor provides data to the power steering, traction control and electronic stability systems. If the coding is off, it can cause all sorts of weird issues, including incorrect power steering assist and stability control intervention. Given the symptoms and lack of recent work, I'd say a faulty or mis-calibrated sensor is the prime suspect. I ended up going to a trusted workshop to get it sorted, probably a good idea in your case too!

Thanks for the info. I had the steering angle sensor replaced. The mechanic confirmed the coding was faulty. Cost me 195€ all in. Steering feels normal again, and no more vibrations. Hopefully, this also fixes any potential issues with traction control and electronic stability.