Our X5 recently had similar problems. First, lots and lots of errors, then it wouldn't start. Had to be towed to the garage. They tried a few things then had to speak to BMW Germany as they ran out of ideas. Turned out to be the main/central computer control unit. This is what they plugged their diagnostics in to to get fault reports. Because that unit was faulty, it was giving inaccurate diagnostic data. Not only did this lead the engineers on a wild goose chase, but the faulty central computer gave all these fake errors and caused the car to shut down. Swapped it out, and the car has been great since.