Dealing With Video Starts and Stops While Watching:

Dealing With Video Starts and Stops While Watching: Three Common Causes and Three Possible Solutions – Ask Leo! askleo.com
The speed of your internet connection is the most important factor when streaming video. Next would be other programs or devices making heavy use of that internet connection at the same time. Depending on the situation, you may be able to pause to allow things to catch up, reduce the demand by selecting lower quality, or avoid streaming completely by downloading the video to watch later, if that’s allowed.