Starting a project from scratch is very difficult. To overcome the mental block, I recommend my clients to follow a simple two-step process: Release and catch.
Step one: Release. You have to let your mind work on its own. Stop thinking consciously and let your subconscious take over. You can do this by doing an activity that relaxes you: cycling, meditating, running, swimming, walking, knitting, fishing, or listening to music. Some people need an hour until the ideas come, others need days.
Step 2: Catch. Once the ideas appear in your head, grasp them by writing them down on a piece of paper. If you don't do it soon, you'll forget them.
Write, analyze, discard and expand, make sketches and outlines.
You will see your project begin to take shape.
Creativity is a process that requires freeing your mind, what we psychologists call broad focus, and centering your mind, what we call narrow focus. You have to change from one focus to another constantly, to move forward when you prepare a new project.
In my sessions and workshops I help my clients through this creative process. My job is to speed up the decision making process and keep them from getting sidetracked. In a two-hour session, spectacular progress can be made.
Remember: First release, then CATCH. And when you are stuck, start again.