Why does Google Search automatically sign me in when I haven't even clicked Sign In in weeks?

Answer 1

Google uses cookies which are configured to have a very long life expectancy (cookies are what keeps you signed into a site when you go off Surfing the internets on other sites). Cookies very often only last the length of your browser session or until you do a "clean up". However, the infamous Google Cookie lasts until around 2038 AD in your browser

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These cookies contain a unique identifier that can link you directly to your search terms. It could also link your searches to your Gmail account, possibly profiling your internet activities and usage.

Check out Google's privacy FAQ for more detail.

There are countless ways to disable/modify the Google Cookie. Without knowing which browser you use and your level of IT competence it's difficult to say which one would suit you best. However, probably the easiest and quickest way is to clean up your browser, including deleting cookies. Remember though that with the cookie removed for the site so are all your personal preferences. If you don't know how to clean up your browser let me know and I will help you - I will need to know which browser you are using though, which is probably Internet Explorer.