Hi wonder if anyone has had this problem, I’ve got a c class 4 years old, I noticed a slight shimming at the back when driving the other day, seems to be more noticeable the slower I go but today I heard a clunk coming from the middle of the back of the car, the cluck slows down or speeds up depending on how fast I’m going, can’t see anything underneath but wonder if any of you have any ideas? Thanks in advance.