Dear JoanS20,
I have read about your situation with your Enclave. I understand how frustrating this must be.
I see that members of the forum have provided you with information to help you try to figure out what is going. If you experience this again and the things that have been mentioned don't work, it wouldn't hurt to contact personnel in the service department at your local Buick dealership. I know this is the "dreaded" take it to the dealership line, but there are a few General Motors dealerships within my area that do provide ideas of what might be going on with a vehicle when they are told that the vehicle is out of warranty or something like that nature.
Sincerely,
Michelle, Buick Customer Service