Kicking into Neutral on its own

new to here. We just recently bought a 2012 Prius. So far seems to be good but we have 1 little glitch. Occasionally when coasting it kicks itself into N. It will go days without doing it, but sometimes when it does it, it keeps doing it. The really weird thing is if you hit the power button and then turn the car back on it quits doing it. Any thoughts suggestions on what this is? And then also how do you know when the main battery is getting bad. The dealer told my GF it’s fine but I hat to sit in a drive through for like 15-20 minutes the other day and it went from full to almost empty. Yes I was running heat. Thanks!

 

what’s the thread for the one you are mentioning? The only thing I was finding on kicking to Neutral was people doing it to change speeds or something, not the car doing it on its own?