a/c shuts off intermitently

I have a 1999 dodge ram 1500 (5-speed). My a/c is fully charged and cools to 45 degrees most of the time. It seems that in stop-n-go traffic or slowing down to get off the hiway almost always shuts the a/c off and only warm air blows. Rarely it will kick-in and get cold on its own again, but most of the time when it shut's off/blows warm, I need to shut the truck off for 5 minutes or so and then restart it. Then the a/c is cold and working again.

:crying: It is too hot driving 70 miles round trip for work with no a/c.

Any ideas?????