Been there a few times, Best referred to as a brown out. Outside lane of M4.
Autobox means no declutch and coast. Got my attention.
All goes dead, engine, instruments, PAS, wipers etc.
In some cases it auto reboots, sometimes you have to reboot and restart.
I would not rule out the dashboard itself. Have you had any work done on or behind it?
If you have ever seen one being removed it is a bit tight back there and refitting it could snag a cable easily.
I believe mine was caught cables behind the dash following the screen bring re fitted due to leaks?
