Hello and welcome to the forum! Although there are no active codes showing, there are likely stored codes that will give you a place to start troubleshooting. When you took it to the dealer, did they run the codes on their system? In case it is the VANOS, I'm including a link to our site's DIY tech article on the procedure to replace it. If you have any questions about the fix or need additional info, please feel free to post a Comment just below the article and one of our techs will get back to you with details. Hope this helps and best of luck!
BMW E90 VANOS Solenoid Replacement | E91, E92, E93 | Pelican Parts DIY Maintenance Article