|Slow internet is usually the cause. While you watch the video, it is downloading more video, if the download speed is fast enough, it will always download faster than you can watch and there is no buffering. Buffering happens, when what you are watching has caught up to what has been download and if buffers (pauses and waits) for more video/audio to be downloaded. Common causes are a slow internet connection on your end, or it could be the server the video resides on is overloaded with traffic and has a hard time keeping up. If this happens on different sights it is likely your internet is not downloading ahead fast enough. Have you tested your bandwidth speed??? Do not do the "before you begin the test scan".....here is a link|
To err is human but to really screw things up, you need a computer!