Some days, I take a Sharpie and a piece of paper and just work out ideas, over and over.
The sheet looks something like this:
I can go on like this for a while...
Just, looking at ideas, trying out characters, thinking about hairstyles.
Every so often some of the doodles want to interact, or hang out with each other...
That's fine, too.
After a while, I will have worked through some ideas, gotten the pen moving, and given myself a break from drawing "something." And I feel I have more energy.
You can apply this principle in most any activity. Try just noodling around on the piano, or on the guitar, or just pounding some clay without making a particular shape. I think noodling and doodling are pretty similar.
Interestingly, you can open yourself up to ideas this way. Because you are letting yourself go, not making yourself go.
I make time regularly to just fill up some paper. Can you do the same thing with whatever you enjoy doing?