Do you have the digital dual zone AC controller? Mine does and the blend door actuator is going bad. Normally I just leave it on 60 degrees all the time. If I leave it on higher than that then the door could get caught by the air from the blower and since the actuator is weak it will push the door to block the evaporator and let the air pass over the heater core. Which makes it blow HOT even though it says it is on 60 degrees. So by shutting off the car and restarting than the door goes back to the original commanded position.
The actuator varies from around $60-$200 depending on what type of control head your truck has.
Mine is the full digital and wholesale price from a Chevy dealer is $180 but Dorman makes aftermarket ones and the one for my truck is $120 from Rockauto.
Hope this helps.