Hi everyone. On occasions, after I fit my seat belt, and the car automatically tensions it for me, I hear what sounds like an electric motor just behind the right hand side of my head. It runs for perhaps a couple of seconds. Is this normal, if so what is it doing? The belt has already tensioned. Car is brand new - 2 weeks - C220 CDI AMG Sport Estate. I only noticed this in the last few days, and am sure it didn't do it previously. My supplying dealer is 80 miles away, although I have a local Mercedes dealer. Appreciate any comments.