Bitcoin is pseudonymous, it can only stay private as long you don't link any information to it.

Once you intend to use that Bitcoin, spending, or selling then any other Bitcoin from that point forth used in the same wallet can be traced.

And even Bitcoin that's mined could hypothetically be traced, see what pool it came from, or if solo mined, and how much is in that wallet.

Monero is better in this regard since it's harder to trace since that information is obfuscated, or anonymized.