2007 Ford Ranger - HVAC

good morning i have a 2007 ford ranger 95k’s excellent shape my dilemna is my AC it takes about 15minutes to cool it is not low on freon as i have checked that out .no leaks however i find that if i turn the knob that regulates the hot and cold for winter purposes to the hot and leave it for a couple of minutes then turn it back to cold it starts to cool and within a minute or two it works great i would like to take it to the AC shop however im very leery about most mechanics if i had an idea of what might be happening i would feel more comfortable in doing so are you able to give me some info thank you Rene D

Probably the blend door is sticking.