Youtube – How to prevent watched videos to be listed in suggestions

Your Internet speed is too low, as you said animated circle, that's indicating you that the video is currently buffering, in another words, it is loading, so whenever you open a video page on YouTube, play it, than immediately pause it, let the video buffer, you'll see a grey line filling, once it's filled, you can play your video without any interruptions.

There are several browser extensions that remove this and/or other elements, if you so choose to.

I use the Magic Actions for YouTube extension, that allows disabling recommended videos under Options > Hide Page Elements. It is available for Google Chrome, Mozilla Firefox and Opera.