AC Problem

What is your question?

hello how are ya guys i just went to the repair shop to check on my ac they take a look at it could not find anything when i drive when i turn on my AC it works fine 30 to 40 min then it stops when i leave the car off for like and 30 min to 1 hour when i turn on the AC it starts working again first i was thinking it has some whole but repair shop could not find anything so what could be the problem that causing this kind of problem