cool turns HOT

is there any help or ideas I have a problem with the climate control I have the A/C or just the vent and then it goes hot like I moved it to the hot side , it was doing it here and there now I cant go 2 blocks and have to shut the truck off while rolling to reset it and goes back to heat again


any info would be very appreciative I am at wits end with this problem...

Probably blend door actuator. GM is notorious for them failing.