Mine does similar when the tank starts getting down about 1/2.
If I'm parked, it'll run down to about 1/3 tank of gas. but when traveling, it seems like 1/2 tank is about the lower limit.
HondaMan also mentioned oil level, this could also slosh around while traveling, make sure its full.
I'm going to add a air vent to my compartment door to help with air flow. The chassis engine puts out a lot of heat. That could aggravate the problem.
2001 Coachmen Mirada (Ford F53 6.8L V10) - Toad 2001 Civic
It won't do MACH 2, but I can get a sandwich and take a pee.