ac only works after running for a while

I have a Crown Vic, 2003, LX. When I start up car, AC doesn't work - just regular air comes out. But after I drive a while and then sit at an intersection idling, the AC kicks on. Any ideas on what might be causing this issue or any suggestions on what can be done to fix it?

Thanks for any help.

First off,

Check the refrigerant pressures in the system. A 14 year-old system probably needs some loving attention.

I would not bet it being low on refrigerant, once low the compressor continually cycles and won't cool very well...

I've had a flakey low pressure cause delayed start up, someone on here had issues with the compressor relay doing same... A inoperative cooling fan can do same but engine should be running hot...

I will check the refrigerant pressure.

It's strange though, once the engine is nice and hot, the AC blows cold air just fine.