2017 Leaf inexplicably shut down while parked

Yesterday, I was under the weather and had the chills, so while I was parked, I turned the driver's seat heat to high, and put on the heater on the highest setting. After 3 or 4 minutes, the Leaf simply shut off.

I thought perhaps I had somehow overheated the battery, but I was able to turn the car back on immediately, and the battery temp was very low. Only 4 temperature bars.

What happened?? My family and I could've died if this happened why on the highway!

It shouldn't as long as the car was in READY mode and there's sufficient charge on the big HV battery. READY mode is indicated via the green car with arrows.

I've had something simliar happen with my 2017 S: pull into driveway, while listening to something excellent on the radio. Put the car in Park, because I want to listen to the rest of the program. If you wait long enough, I think the car shuts itself off, because it thinks you forgot about it.

I can't recall for certain if this happens when you shift to Park and wait, or if you double-tap the power to put the car in accessory+heater mode. But it's happened a couple of times to me, both times while I'm sitting in the driveway. ... definitely NOT while driving.