That is not normal for any vehicle.
It could possibly be a low level of coolant in the radiator. I've had
this happen before. My old Dodge Van had a slow coolant leak. During
the winter it would do exactly what you're talking about if I didn't
keep the radiator topped off.
When the radiator isn't full, there won't be enough liquid in the
system to circulate through the heater core, which is what transfers
the heat from the cooling system into your vehicle. When you start
moving, naturally the engine speed will increase, which helps circulate
the hot liquid through the heater core...Thus the heat suddenly starts
I'd check that first. By the way, you want to add coolant only while
the engine is running and is up to full operating temperature.