Personally, I'd bag the snake securely, & put the bag (with a little padding for comfort, like a towel, in case you have to stop fast, etc) into an ice chest to protect
the snake from the A/C that you might want to run for yourself, and from excessive heat (from sun coming thru car windows) that can harm or even kill a snake.
I've moved halfway across country with my snakes this way, no problems at all. If you want the snake to be kept a little warmer, fill a plastic bottle with warm to
hot water and put that under the towel in the ice chest with the snake. If you use a pillow case for a snake bag, the snake will be able to move around some to
choose the extra warmth inside the "ice chest".
Caution about "just bagging the snake & put it out of direct sunlight": when you drive, the sunlight comes into the car from all different angles because
you're moving & cannot mess with the bag while driving. AND I do know of someone who intended to do a good thing, putting their bagged snake on the
floor of the truck ("out of direct sunlight") where it overheated from too much engine warmth rising thru the floor & later died. So PLEASE use a styro-foam
box or ice chest to protect your pets in travel? That's not asking much, is it?