I recently upgraded to Ubuntu 18.04. Since the upgrade, my laptop sometimes won't wake up after being suspended (usually after it has been suspended for longer). When I open the lid, no lights go on. Pushing the power button does not cause the laptop to resume. I am forced to hold the power button for 10s to force a shutdown and then boot.
This laptop doesn't have a discrete graphics card so that is not the issue here.
My laptop is a ThinkPad X1 carbon gen 5.
$ uname -r 4.15.0-22-generic