It’s not strictly a password, it’s a recovery key for the encryption. The drive is unlocked automatically at boot by the key residing in the TPM, if the system “hasn’t been compromised”

Bitlocker is enabled by default on new Windows installations, and you can run into this situation by resizing partitions or messing around with your EFI partition. Disabling secure boot without disabling bitlocker first will result in this.

Make sure you have your recovery key, or completely disable bitlocker until you’re done provisioning your system (or uninstall windows altogether)