While driving my 2024 Cadillac Lyriq in rolling traffic, the vehicle abruptly engaged the brakes without warning or cause. The braking was so forceful I initially thought I had been rear-ended. Once the braking event ended, I began to acceleratea”only to discover the vehicle had shifted into reverse without any input from me. This resulted in a rear-end collision. There were no alerts or dashboard warnings to indicate the gear change. I believe this may be related to a malfunction in the automatic emergency braking system or the shift-by-wire controller. This behavior presents a serious safety hazard and must be investigated. I have filed a report with Cadillac and will be taking the vehicle to a dealership for diagnostics and data log review.