One of the most useful things you can do for any project is show it to other people. Even if all you have is an idea, show that to people.
An idea is a project in and of itself. When you explain it to people in one sentence, what do they think of? What do they picture? Try a slightly different explanation the next time you explain it to someone else. You’ll notice how even in your own mind this slight change in description changes the entire mental trajectory of the project.
If people don’t ‘get’ the idea of your project now, will it be any more comprehensible once you have something down on paper? Will it ever get any easier to explain?
If you don’t want to show it to someone, what’s the reason behind that? Does explaining the project reveal cracks at its core? Are you holding on to the idea too tightly and you don’t want it to change? Is it because the next 6 months of your life are built around it and you’re scared to lose any whiff of certainty?
Pretty much everyone I know who’s serious about working on something starts showing it to people they respect from the start. People with more experience also recognize this as a sign of commitment, and are often willing to help for that very reason.
If I’m not showing something to people I respect, it’s probably because it has some flaws I’m not being honest with myself about. And it’s better to find those sooner rather than later. Show off or shut down.