Seems like cache is automatically gets clearing.

I will recommend to perform some experiments :-

1. Remove 3rd party applications which are not required from Add or Remove which cud be found within control panel. Check if it solves problem

2. Close antivirus for 5min. Check if it solves problem

3. Reinstall Firefox. Check if it solves problem

Details like websites remembering you (log you in automatically) are stored in a cookie.

• Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Tools > Options > Privacy > Cookies: Exceptions

In case you are using "Clear history when Firefox closes":

• do not clear the Cookies
• do not clear the Site Preferences

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/Clear+Recent+History

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords.

Clearing cookies will remove all specified (selected) cookies including cookies with an allow exception that you would like to keep.