When you use a browser and go to a web site and logon the logon information is normally held on your PC in a "cookie".
Next time you go back and visit the web site the "cookie" information is used and this saves you logging on again.
It sounds as though you (or someone else) may have changed a setting on your PC so that everytime you exit the browser the cookies are deleted, or maybe everytime you turn off the PC the cookies are deleted.
Are you aware of changing a setting like that?
Check your browser settings and see if it is set to delete cookies after exiting the browser.