There are a number of errant messages that pop up during start of vehicle caused by slow or unresponsive modules. You will get miscommunication or bad packets but the car will still operate normally. GM has been hunting these issues down slowly.
However, if you take the vehicle in now, there is a new TSB with an update procedure where the dealership HAS to update every module in the vehicle to the most recent versions and verify all communicate correctly on every visit to make sure vehicles are at proper spec.