On 4-5 occasions since purchasing a new 2021 GMC Yukon Denali the automatic breaking function has engaged for no reason, with no obstruction in the roadway. It has occurred at low speed (after disengaging break and starting to drive), as well as on the highway at high speed. Obviously, this is a major safety issue. I had the car in to service last year and they said the move the toll transponder. We did that. Subsequently, this issue has occurred multiple times. So yesterday, I called and spoke to service team at the dealer. They said to bring the car in and move the transponder further away from the center of the top of the windshield. We removed it. I asked him to note our file and he said we had to have the car in to service to do that. He said to call GMC at 800-462-8782 and report the issue. So I called the # and asked them if this has happened to other owners and she said she could not tell me and she could not note her file either. So we will bring the car in to have the service dept run a diagnostic. I will attempt to disengage this function by reading the manual.