AC only cold when driving, warm when stopped

2004 S type 3.0L. When driving the AC is ice cold, when stopped however the air that comes out is warm. What could that be? Any tests that i can do to narrow down the possibilities? maybe a fix i can do without bringing the car to the mechanic?

Thank you for any help

Your A.C may need recharging. I have a Venture but when it came back after an engine rebuild my A.C went missing..nothing, absolutly nothing so I recharged it and it works great now.

Also, the AC condensor in frnt of radiator canbe plugged with leaves + Bugs.
The fan should be ON drawing cool Air through both the AC condensor +
Radiator keeping your car cool.