Heater Flap Motor problem

Hi.



I have an issue with the motor that moves the flap that directs air to control hot or cold.



Currently to change from hot to cold I have to turn the car off and then back on to get the motor to move the flap.



But once it's done it's first move I have to put temp up or down, restart car and the flap will move again.



Does anyone have any idea why it's not moving the flap once the car is running? Would the internal temp sensor be causeing this?



Thanks