Strange behavior

I am having a weird issue with the Prius. The last few days when I am finished driving, put the car into park and hit the power switch, I appear to lose all 12 volt power. Interior lights will not turn on, I can not use the key fob to lock and unlock the door, and nothing happens when I press the power button. Sounds like a bad 12 volt battery right? But then when I open the door and shut it, the alarm goes off. I still can not use the key fob at this time to unlock the door, and the power button seems to turn itself on on magically. It has the amber light on it so i would assume it is in accessory mode. If I then press the power button again, the car turns off and I have power. The lights will turn on in the interior, key fob works, and the power button works. This also seems to wipe the memory of my radio, and the MID.

I am at a loss of what to do with this.