Car died at traffic lights

[akkers5]

I have a 420d/UK 2018. I was driving along yesterday and stopped at traffic lights. The engine went off as usual with the on/off setting. As I knew the lights were going to be long I put the handbrake on and put gear into P mode.
When the lights turned green I put my foot on break pedal hoping engine woul start up, but no, nothing. So I pressed the start button when dash lights came on and pressed it again to start engine but nothing (dash lights went off).There were no warnings or anything on dash. I tried starting several time but nothing. I put hazard lights on and started to ring for help. There were a couple of pedestrians who volunteered to push the car but I told them could not get it into neutral hence not possible to push.
After about 10 mins of panic I tried again and engine started up and I was able to drive off. I turned off the on/off button so that it did not switch off at coming junctions. I got to the destination ok and parked. After about 2 hrs I came out and started engine ok but for a 2-3seconds engine made a whirring noise. I drove back ok without any further problems.
What happened here? Could it happen again? Has it happened to anyone else?

Edited by akkers5 on Tuesday 19th August 16:08

[rottenegg]

1) When was the battery replaced last, if ever?

2) Get yourself Bimmerlink, and then you can answer your own questions.

3) I'm surprised the yanks didn't file a class action lawsuit against BMW for removing the emergency Neutral function. Dumb arses. Probably only saved £8.37 per car.