I think you may have misunderstood the way that Bitwarden is normally used, or you may not understand the important distinction between vault locking and logging out.
Locking a vault means that all sensitive data are purged from your device memory, while the app or extension retains a cache (stored on the hard drive) containing a strongly encrypted copy of your vault contents and keys. Logging out means that the encrypted vault cache is erased from the hard drive.
Normally, users would keep their Bitwarden apps and browser extensions logged in indefinitely; only in extreme situations would it be advisable to routinely log out of all apps and extensions.
If you have logged in to your Desktop app once (and set up the Desktop app preferences as I described above), then you will will not have to enter your master password into the Desktop app again, with a few, rare exceptions (e.g., if you go to the Web Vault to change your master password or to deauthorize all active login sessions, or if Bitwarden performs some back-end maintenance on their servers that requires deauthorization of all users’ login sessions).
To make sure that you do not log out of your Desktop app, make sure that you have set the “Vault Timeout Action” to “Lock” under File > Settings:
Likewise, in the browser extension, go to Settings > Account Security and ensure that the “Vault Timeout Action” has been set to “Lock”: