I have slept in minivans several times in the winter. Here are my observations.

First of all, you will get a much better night’s sleep in a motel.

In cold weather, I wore a stocking hat and slept in a mummy sleeping bag. I was never cold.

You need to crack open a window or two for ventilation.

I slept in rest areas that had a security guard on the premises. You’ll be hard pressed to find these. Tennessee has some. Don’t sleep way off on the end alone. If anything makes you feel uneasy, leave. Trust your instincts.

I stick to busy rest areas with plenty of cars and traffic.

Your sleep will be interrupted by headlights, lot lights, engine noises, truck noises, doors slamming and people talking. A mask would help with the lights.

The inside of your vehicle will get humid. Droplets and even frost will form on the inside of the windows.

You MUST be able to lay flat and/or on your side, however you normally sleep. You might need to pad areas with towels or camping mats or whatever. Figure this out before your trip.

Be prepared for something to wake you up at least once. My dog woke me up at 3am!

One night of this is enough.