Ever since upgrading from 17.10 to 18.04, I've struggled with this odd issue: when the laptop wakes up from sleep and I enter the password, it freezes - only shows me the default Ubuntu purple screen and an immovable cursor that doesn't look like my theme-set cursor.
I had a problem with 17.10 as well, but not as annoying - when waking up from sleep, I couldn't move the cursor for about 15 seconds, but otherwise everything worked fine.
Another problem that may be related but that I cannot reproduce: sometimes (while using the computer), I see the "Computer will suspend due to inactivity" notification and then it suspends itself. Usually, when trying to wake it back up, what I mentioned above happens, but once something else happened: it managed to wake up, but my session was gone, as if I had just rebooted.
I have an ASUS ZenBook UX410UQ.
I have the same problem but, here, I have accidentally found a work-around: I leave an 18.04 bootable USB stick mounted, and as long as it is left there, resumption is faultless. Should I dare to remove it, the problem appears again. I know it sounds crazy but I can assure you it works, although I cannot offer an explanation as to the why.