Thanks for the bug report. First, please follow these instructions to check for crash reports which might explain the issue: https://wiki.ubuntu.com/Bugs/Responses#Missing_a_crash_report_or_having_a_.crash_attachment
Second, next time the problem happens please: 1. Wait 10 seconds. 2. Reboot. 3. Run: journalctl -b-1 > prevboot.txt 4. Attach the resulting text file here. ** Package changed: xorg (Ubuntu) => ubuntu ** Changed in: ubuntu Status: New => Incomplete ** Summary changed: - Xorg crash + System freezes -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1934450 Title: System freezes To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1934450/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp