AC blows cold only when driving – stops at red lights

I'm melting here in my 2012 Chevrolet Trailblazer. The air conditioning works perfectly when I'm driving on the highway or moving at decent speed. But as soon as I stop at a traffic light or sit in bumper to bumper traffic, the air turns warm and humid. Once I start moving again, it slowly gets cold again. I've already checked the coolant level and the radiator fan seems to be spinning. Someone told me it could be a clogged condenser or the AC fan not working properly. I need proper car AC repair Dubai that can figure out why it only works when the car is moving. I saw Dynostar's AC page and they mention checking fans and pressure. Has anyone here had this exact symptom and found the fix was something simple like a fan relay or a dirty condenser? I'm hoping it's not the compressor because that sounds expensive. Also is it safe to drive like this or could I damage something? Any advice before I take it to a shop would be awesome. Thanks.