The sleep routine (which I have set to engage from 11pm-6am) will auto engage once the device reboots. I have also had it occur at random times throughout the day.
Did you report it as an issue? Since it could be a bug in the beta which would be better if you report it that way they can get the logs as well fix it when it happens
In the Beta Feedback you can select the category you think your issue is.
As well check that the logs part is checked so it's also sent and explain in detail your issue and the steps to reproduce even better if you can get like screen shots or a screen recording.
