The easy part is that your hair is wavy. That's not something that subject to change. It's true all the time. Choosing between "turns" and "turn" is a matter of perspective. If you're focused on the fact that it has always been wavy and always will be, use the Simple Present with "turns." If you're focused on how founding out that your hair is wavy was a revelation to you, use the Simple Past "turned." Just remember that either way, it's an informal conversational style to leave off the subject like that. In writing, you would want to include "it" as an empty subject unless you made it clear that you were directly quoting someone's spoken words.

In your sentence, both present and past can work, but they convey slightly different nuances: 1. Present Simple: "Turns out that my hair is naturally wavy." * This sounds more immediate, as if you've just made the discovery, and it's a fact you're now aware of. 2. Past Simple: "Turned out that my hair was naturally wavy." * This reflects that the discovery was made in the past, and you're narrating it as something that happened. Present simple is more natural here if you're talking about a new realization that's still relevant.

^^^ that's subject to change ^^^