I went to reboot my machine (18.04 LTS) and it's stuck at the MATE logo with the scrolling 5 dots and a message underneath that says:
Unattended upgrade in progress during shutdown, please don't turn off the computer.
Progress 95.3488% (linux-image-4.18.0-20-generic)
It's been that way for going on 15 minutes. Suggestions welcome.