In often find in times of creative block that something I don't understand is trying to get out. When this happens I like take out one if my favorite pens (usually a Micron 05) and do a few blind drawings. I let my mind wander and I stare into space and let my hand move where "the spirit" wills it.
The results are sometimes interesting, probably only to me. But I like the thought that creative energy flows through and makes what I don't have the comprehension or courage to make. At times I'm surprised at what's on the page either because it resembles something or happens to be inspiring. I would say its akin to seeing shapes in the clouds, except I made this cloud.
I've never been a fan of scribbles in art myself, because they just seem to be a cop out. And yet I find so many works in museums that appear to be just that. Anyone who's attended art school for any length of time can tell what a last-minute work looks like and sounds like.
However I can see the value in such an exercise. It is very freeing, it loosens up the muscles, a warm-up if you will. We often did quick sketches in college for just this reason.
One of my favorite writers on art and creative processes, Julia Cameron, wrote a couple of things that I ponder daily when making art. One must be willing to make bad art, and one must create at all times, not just when "the mood" strikes. Among the great many artistic truths she writes about in her many books, I find these two to have been the most helpful to me in getting to work. Fear of perfection should not hinder progress. Fear of any kind should not stop you.