It's probably a sensor gone bad. Your warranty will make it right. It is frustrating to have random faults like this. Thankfully my car hasn't misbehaved, yet, and I'm at 80K.
2008 535i - Monaco Blue/Tan Leather, Sport, Premium, Cold (+ heated rear seats), Navi, HUD, PDC, CA, Sunshades, Fold down rear seats, CPO, Extended Maintenance