A/C eradically blowing through wrong vents

[Chino2ua11]

While driving the ac will quit blowing through dash vents and will switch to floor and defrost on my 08 Tahoe. If I stop and restart SUV it will blow the way it suppose to for awhile, but usually will divert back to the floor and defrost again. So you see I do alot of stopping and restarting the car.. What is causing this???

 

[Chino2ua11]

Same,

C'mon, there is nobody that has heard of this before.....