How to remove automatic log-in facebook

if you mean every time you go to facebook, youll be logged on, theres a simple way to fix it:
-go to facebook
-logout
-when you next log back in, DO NOT click the box that says "remember me"
-and log out after every time you go on :)

Did you try deleting cookies before you try, or contacting facebook?

It is weird, but in anycase, but you can try deleting your browser cookies and private data  to see if that helps.

Have you scanned your PC with Anti-malware/Antivirus softwares?It might be due to virus infection. Are you using an updated browser?Does this happens in other browsers too?If,yes then you have to run antivirus software to remove malwares,viruses form your computer.