Why does AC switch from blowing cold air to hot air without warning?

What is your question?

My 2004 Yukon AC blows nice, cold air, but without warning will start blowing hot air, sometimes almost immediately after starting engine, or an hour or two later while driving. Sometimes, it will blow hot air on the passenger side, while blowing cold air on the driver's side, and eventually blow hot air on both sides. This problem started about four years ago. I noticed that if I turn the engine off for5 or 10 minutes, the AC works again when I restart the engine. The fan is working properly, and the temperature of the AC is consistently cold, until it begins blowing hot air.

What makes this problem better or worse?

If I turn the engine off for 5 or 10 minutes, the AC almost always works again, when I restart the engine.

How long has your 2004 GMC Yukon had this problem?

4 years