JBW - Sounds like you may have the dreaded ZF transmission failure coming on. Good luck getting BMW to do anything. Once its out of warranty they only want to sell you a new tranny. My suggestion is find an authorized ZF transmission rebuilder/parts provider to properly diagnose it. BMW dealers DO NOT repair tranny's, they just replace them. A rebuild will run around $3K. When mine was going out, I got the whine, several fault code incidents, and then the dreaded THUNK when starting from a stop. As I've written elsewhere, the failure mode is a cracked clutch housing inside the tranny. It starts slowly BUT CAN LEAD TO CATASTROPHIC FAILURE, that could endanger your life (pulling out into traffic and it fails, or the tranny coming apart at speed and dumping fluid under your wheels). I do not recommend you keep driving the vehicle. Get it to a knowledgeable shop immediately, AND if you have the problem, REPORT IT to NHTSA at Home | National Highway Traffic Safety Administration(NHTSA) | U.S. Department of Transportation. If they get enough of these reports before someone is killed or injured, MAYBE BMW will figure out they have some liability here and step up and do the right thing and FIX these. Keep us posted what happens.