If the video is stopping and starting, it's more than likely a buffering issue with your internet provider and/or your computer. This will happen even with high speed internet connections. The information from the player is coming in faster than your computer and/or internet provider can handle and therefore it "buffers" the video until it has time to load. Here are two options you can try.
Press Play, walk away, and let the video play until the end. After returning to your computer, press Play again to start at the beginning. The other option is to press Pause, walk away and press Play about 15 minutes later.
These two options will give your computer and internet provider an opportunity to load the video in it's entirety and you should be able to watch it without any buffering problems.