Your internet connection may not be sufficient to watch the video stream or your computer has insufficient computing power. If necessary, you can reduce jerking by closing other active programs. For smooth playback, you need an Internet connection with 5 Mbps for SD channels and 10 Mbps for HD channels. You can check the speed of your connection here.
If the picture on your Apple TV 4 jerks, manually set the resolution to either 720p50 or 1080p50.