1. You don't have an integrated GPU, do you? I am reminded of bug 1705369.
2. In case something is crashing, check /var/crash for files and run 'ubuntu-bug YOURFILE.crash' on each. And tell us here the IDs of new bugs created.
3. As soon as the problem happens again, please take a copy of ~/.local/share/xorg/* and attach them here.
1. You don't have an integrated GPU, do you? I am reminded of bug 1705369.
2. In case something is crashing, check /var/crash for files and run 'ubuntu-bug YOURFILE.crash' on each. And tell us here the IDs of new bugs created.
3. As soon as the problem happens again, please take a copy of ~/.local/ share/xorg/ * and attach them here.