Many people have asked questions like yours, and I've answered a bunch of them. Get an NDA if you want.

But the truth is, most people are too busy with their own pet ideas to bother with yours.

You're in love with it.

We have other things on our minds.

I wrote a blog post with a nifty 2X2 chart in it to explain how, most of the time, you're safe:
https://www.salestactics.org/sharing-new-business-ideas-trust-and-ndas/