My car did this too. It was really annoying and the techs had a really tough time figuring it out. Turns out that the front passenger side spring wasn't sitting in its perch properly. Once they fixed that the noise went away. Ask the dealer to check it.
E90 335d LeMans Blue, M-Sport, Exec, Premium, Nav, 260s
E93 M3 Space Grey, Fully loaded
If I lived in Germany, I'd be proud to drive domestic!