Audio unit goes off/on briefly after car start

2012 Prius Gen 3. When the car is started, the audio unit display will go blank, then it will come on for a second, then back off for a few seconds. While it is doing this there is no sound. This continues for a minute or two and then the unit comes on and works fine from there with no further issues until the next time the car is started cold. Everything else on the car seems to be working OK

Is this an auxiliary battery issue, a problem with the head unit, or any thoughts?