The Primary (Master) Password is only asked when the Password Manager is called on. If you are using sync or accessing a web page that needs a password, this is the cause of your issue.

Thank you, I did not realize I had sync turned on. I may have used it once to try and transfer my logins from an older computer.

When you enter the Primary Password when prompted then you log in to the Software Security Device (Password Manager) and you unlock the passwords and have access to the stored passwords until you log out of the Software Security Device. You can logout of the Software Security Device (Password Manager or about:logins) by canceling the dialog to enter the Primary Password like you get when you click the eye icon to reveal a password on the about:logins page (you may have to close and reopen about:logins) and Firefox will prompt you once again for the PP when required to access the logins. You can test this by reopening about:logins what would give you a PP prompt. For Sync, supplying the PP to login shortly after startup is only a one time action and you can cancel a PP prompt on about:logins to re-lock the logins once Sync is connected.

You can also log out of the Software Security Device by clicking Cancel in a primary password dialog to protect the passwords against viewing and force having to re-enter the PP again. You can manually log out in the Security Device manager.

• Settings -> Privacy & Security -> Certificates ->
  Security Devices: Software Security Device: Log Out button in the right sidebar