I got a black dash screen yesterday too when getting in. Waited about a minute for it to come on, then was just starting to do the reboot sequence when it finally came on.
Been getting a lot more error messages the last few days too. A new one today ("Regen limited"). Headlight error is nearly every time I get in the car now. Sensors blocked maybe every other time.
And for the first time, the I got the "shake key" message. The rear and passenger door handles wouldn't present, but the driver did. Got in and saw that message. Put it in gear the Park, shook the key, hit the fob unlock button many times, finally the doors presented.
Got home and popped the fob battery out. Measured at 2.85v. Just put in a new one that measured 3.35V. I'll see if it happens again.