Ok so I finally got around to looking at this - took the battery out and charged it fully again (brand new battery) and when I put it back in, the car started right up. Went to menu 9 and the voltage while off was 12.4 which make sense bc it just came off the charger.

the behavior was weird when it died, which brought me to post here, bc it was sudden - almost like a fuse blew and everything shut off.

now im curious if I have a parasitic drain going somewhere - I installed a new alternator (DIY) and a new battery. any tips on looking for an electrical drain?

I'll check tomorrow morning to see what the battery level is at

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Garage:
1997 E36 M3/4/5 Arctic Silver
2004 E53 X5 4.4i Titanium Silver
2006 E60 525i Black
2000 E39 540i Black Sapphire