Question...have you been having steering wheel lock issues? To me it sounds like your steering lock mechanism (common on 2006's) is jamming and not unlocking the wheel, which won't turn over the car. I had to get that fixed on mine. Had to literally jerk the wheel hard to get it to unlock, and sometimes got a red icon with a lock on the OBC.
I've also had my starter replaced on both 2006's I have. Reason being was the starter wasn't disengaging soon enough and was grinding. Notice any of that?
2X 2006 BMW 325i [Electric Red & Mystic Blue] | ZPP | V1 | Rear Fogs | M3 Lip Spoiler | EAS RemoteKey | BMS Powerbox | Projector90 Headlights w/ LED AE | LED plate lights | OEM Blacklines