A detail like a website remembering you (log you in automatically) is stored in a cookie.

You can use these steps to make a website recognize and remember you:

• create a cookie allow exception with the proper protocol (https:// or http://) to make a website remember you
• use "Delete cookies and site data when Firefox is closed" to let cookies without allow exception expire when Firefox is closed
• Options/Preferences -> Privacy & Security
  Cookies and Site Data: "Manage Permissions"

In case you use "Clear history when Firefox closes" or otherwise clear history.

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

• Options/Preferences -> Privacy & Security
  Firefox will: "Use custom settings for history":
  [X] "Clear history when Firefox closes" -> Settings
• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

• clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows, and software installation and exception for password and other website specific data
• clearing "Cookies" will remove all selected cookies including cookies with an allow exception you may want to keep

A detail like a website remembering you (log you in automatically) is stored in a cookie. You can use these steps to make a website recognize and remember you:

• create a cookie allow exception with the proper protocol (https:// or http://) to make a website remember you
• use "Delete cookies and site data when Firefox is closed" to let cookies without allow exception expire when Firefox is closed
• Options/Preferences -> Privacy & Security
  Cookies and Site Data: "Manage Permissions"

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In case you use "Clear history when Firefox closes" or otherwise clear history.

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

• Options/Preferences -> Privacy & Security
  Firefox will: "Use custom settings for history":
  [X] "Clear history when Firefox closes" -> Settings
• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

• clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows, and software installation and exception for password and other website specific data
• clearing "Cookies" will remove all selected cookies including cookies with an allow exception you may want to keep

EDIT: The option "Delete cookies and site data when Firefox is closed" was checked and that was the issue. Thank you for your response. Solved!

OUTDATED REPLY: So I just checked all these settings. They look fine. I don't clear anything on closing Firefox. Why does Firefox behave differently only on my second profile? Same settings on the main profile and it remembers my login information on all websites

Does Firefox still have the persistent Google cookies at startup in the work profile? You can use the "Manage Data" button to get a count of cookies and size of DOM storage data per site.

But more generally, does your work account set a persistent cookie for your session authentication info? If the site only sets a session cookie, it will be flushed automatically when you end your Firefox session regardless of other settings.

It may be possible to retain session cookies if you set Firefox to automatically restore your previous session and you leave your Gmail open when you Exit Firefox.