Youtube alrady has the feature of creating automatic playlist for us to watch videos related to the video being played. So, why autoplay? I don't know, but it's very annoying (mostly, too attention grabbing).

If you are like me and hate yt taking your attention from you, you should checkout this other script: https://greasyfork.org/en/scripts/369978-remove-annoying-right-column-youtube ;)

Have a nice day!

Credits: the code is based on https://greasyfork.org/en/scripts/7893-remove-youtube-autoplay, thanks to @wxc (https://greasyfork.org/en/users/8868-wxc)

Scripts Github repository: https://github.com/helq/helqs_userscripts/