I had the same issue on our November 2013 build S85 back in December 2019 but with the added warning message of "Regenerative braking system disabled." I called Tesla Roadside and they instructed me to drive to my local Service Center before attempting a reboot (so the car wouldn't have to be towed if it failed to restart). The car did restart, but the issues remained. A quick diagnostic of the logs showed the need to replace the HV contactors. They also replaced the HVAC drain hose, 12V battery, and drive unit while there at it (whining rotational noise was getting pretty bad over the last 3 months).
I have an Anker ROAV 12V battery monitor and it showed no signs of a worn 12V battery, but I'm assuming a failing HV contactor might have placed more strain/stress on the 12V thus the replacement...that or Tesla was checking all the boxes to make sure I wouldn't be back soon after.