There a few reasons for what you are experiencing. The hard drive could be failing, doubtful. If you are viewing it over the internet there could be to much. Lastly it is because of the way you are recording. Motion clips put together will look choppy as the player goes to the next clip. That is because there is a stop and new start point. 

Does this happen when you look at 1 clip only, or is it when you playback multiple clips together?