Probably a blend door/actuator related problem. I assume since you haven't mentioned anything about it happening only on one side that you have single zone climate control. The blend door is located behind the center stack in the dash.
The blend door actuators are reversible, 12-volt direct current (DC), servo motors. Models with the single zone heating-A/C system have a single blend-air door, which is controlled by a single blend door actuator. Models with the dual zone system have two blend-air doors, which are controlled by two blend door actuators.
The blend door actuator (1) for the single zone heating-A/C system is located near the center of the HVAC housing (2), close to the dash panel.
For the dual zone heating-A/C system, the same blend door actuator used for the single zone system becomes the driver side blend door actuator, which is mechanically connected to only the driver side blend-air door. A second separate blend door actuator (3) located on the top of the HVAC housing is mechanically connected to the passenger side blend-air door.
All actuators (1) are interchangeable with each other. Each actuator is contained within an identical black molded plastic housing with an integral wire connector receptacle (2). Each actuator also has an identical output shaft with splines (3) that connect it to its respective door linkage and three integral mounting tabs (4) that allow the actuator to be secured to the HVAC housing. The blend door actuators do not require mechanical indexing to the blend-air doors, as they are electronically calibrated by the A/C-heater control.