1. If you have Custom Settings AutoFocus a1 set to Focus, the camera shutter is not supposed to fire unless the subject is in focus. Therefore the camera would not shoot continuously.
2. If your settings for shutter speed are to low or for lack of light, your camera would probably not focus most of the time. Lots of other settings or combinations could be the cause. Do you have your D600 set for continuous focus, AF-A, AF-S, or AF-C? Are you letting the camera select the focus area or are you using single spot? Are you using auto white balance? etc. etc. etc.