Yes, babies are born with both the sympathetic nervous system and the dorsal vagal nerve ready to rock. They have access to fight/flight/freeze, but they do not have access to social engagement and self-soothing, which are governed by the ventral vagus. This must be learned. If a baby is distressed all the time, that is a good sign that their sympathetic nervous system is in overdrive. If they are super calm and pretty unresponsive, this most likely means that their dorsal vagus is on overdrive.