Unstrung! especially if in a vehicle. In Maine, you probably don't have to worry about the heat delaminating a bow like we do here in Florida, but when in transport, I keep mine unstrung and in a soft case in the cab of the truck to keep it from getting "dinged up".
I have the luxury of having a crew-cab pickup, so mine rides horizontally on the back seat with extra clothes and other soft gear around it.
If you want to keep it in the bed of the truck, I'd look into a hard case of sometype.
Good luck this season maineac!
John