Starting/stopping or choppy playback is typically due to problems with your internet connection. Fortunately, checking your internet connection is very easy. Simply go to http://fast.com, a service provided by Netflix, and it will tell you have fast your connection is. Anything less than 5mbps will likely lead to a poor viewing experience, and any number with kbps will result in an extremely poor viewing experience.
Clear Your Cache: Go into your browser settings, find clear browsing data, and clear your cached images and files. We find that this fixes most problems!
Mobile Devices: Make sure that you are on wifi, as it is typically faster than your devices data connection.
Computer: Reboot your router. Routers need to be restarted occasionally to maintain the best connection speeds. To restart your router, simply unplug the power, wait 5 seconds, plug it back in, and wait a few minutes for the system to come back on. Go to http://fast.com again and check your speed once you are back online.
Most internet service providers (ISPs) provide internet speeds of at least 10-12mbps. If you're getting less than that, contact your ISP and ask about improving your internet speed.