You know, I have the same problem.

I find, for me, that it's best to set aside some time before bed, about an hour, for free doodle. Just me, a pencil, and a drawing pad; and no particular direction.

of course, I am eyeball deep in trying to get my relaunch up and running, so it tends to just be my characters in various poses and outfits doing random things. Or, sometimes, thumbnailing ideas for future stories. But, basically, it's just straight ahead sketching of whatever for at least one hour.

That seems to help me, a lot.