When I first start or if I idle for a while the AC stops making cold air. I suppose the compressor stops. I have had two suggestions - a monitoring switch is bad, or the freon is low. But recharging the AC does not solve the problem. The AC works fine at highway speeds for more than a month after last AC charge.
You didn’t say from whom the two suggestions came, but I suggest you locate an independent automotive AC shop in your area and let them have a look at the car. These folks are the experts, and have the equipment and knowledge to correctly diagnose and repair your car’s AC.
All components of the HVAC system can be tested to determine what is working correctly and what is not. Testing is the correct way to determine the problem. Guessing is not.
If the refrigerant was not added by a professional, I suggest that you may want to consult a professional. Too much is as bad or worse than too little. It can also be dangerous to do this yourself.
Have it checked to assure it is not now over charged.
You also want to make sure that the second (radiator) fan is coming one when you turn on the A/C