Ours did that when we were camping in the 20's and 30 degree range during our yellowstone trip. I suspected the deadband range of the thermostat was too narrow but like ya'll, it's in the 90"s so I have somehow forgotton about it...
In reality, some thermostats have adjustable deadbands that when set for, say 70 degrees, don't turn off the heat till an adjustable temp ABOVE that point, say 72 degrees. By widening that range the heater will stay off longer between cycles. The down side is... pull up the covers, heater comes on, kick off the covers, heater goes off...repeat all night long...