I noticed your logs are filled with CUE files, which are not supported by Volumio. This was already mentioned in this forum topic.
Your logs also show repeated MPD errors like:
error: MPD error: The expression evaluated to a falsy value:
These are most likely triggered by the unsupported CUE files. As a result, the library scan fails, and the database isn’t saved, so after a reboot, your music library appears empty.