My wife and I have felt what feels like the seat back moves up when braking. But the seat back is not lose and it only happens when braking. Anybody have this problem or felt the same thing?

i know exactly what you'r saying- mine does the same- but ONLY when its a harder brake, not with usual brake- it seems like the system is getting prepared for presafe braking-- i have experienced pre safe brake; very cool yet freaky feeling and the lumbar was the first to activate..

Mine does that more often that I would like, but I have a gl63 and my driving is a little harder.

Thank you. Yes, only when hard braking. We thought we where crazy. So was this confirmed by the dealer?