The best way to start is just to start.
Start writing. Anything. Don’t worry if it’s something you’ll keep or throw away.
Sketch, draw a circle and make it a face. Add a bit of costume. It doesn’t matter if it goes in the trash.
If the blank page is intimidating, make it un-blank. Throw something on there to tame it. When you do you might find a nugget of an idea. A seed that takes root. Or maybe just a moment that you needed to clear your head before moving on.