I had this on a 4.4, which was diagnosed by BMW in the UK as the stock BMW battery failing. They replaced the battery and I never saw the problem again.

To be 100% clear here.

My car would do this to order if I left it parked facing uphill for a few hours. When I called BMW they asked if the car had been left facing uphill? When I said yes, they immediately said it would be the battery and that it was a known fault with some BMW batteries.

When the car was parked facing uphill a plate in the battery would short causing the car to drop into 'limp home mode' this would always trigger the Transmission Failsafe Message and limp home. If I restarted the ignition then the message would clear and all would be fine until I parked facing uphill.

Good luck.