i suggest taking out a fresh sheet of paper (notebook is fine), putting on music, and letting your mind wander. know that you'll throw away the sheet of paper in the end anyway, free up your mind, try and get your brain thinking right, and you'll find you create some random things. expecting anything out of it puts pressure on yourself. just let yourself be free and let your wrist and fingers do what they want.
or, of course, you can also do a formal piece. or doodle.
it's up to you; i personally enjoy the doodling much more, as i hate my current art style and am trying to find ways to either improve or come to terms with it.
good luck! :))