Why should you disable the master password?
Your master password unlocks all your other passwords. If you disable it, you can also use a normal textfile, bacause if I know the filename I know all your password and probably your digital life
Your windows password by default don't encrypt your files and so your files are unprotected for hackers. At the moment I am studying Computer Security and I don't want to go now very specific, but for your privacy and safety leave the master password activated. You can change settings in Enpass, so Enpass will not be automatically lock up.