Before I started working with newborns, I wouldn’t have believed how much noise they can make in their sleep! I’ve heard many newborns cry in their sleep, even for a few seconds, but they aren’t awake, and still have their eyes closed. They may settle back to sleep on their own easily, if they aren’t disturbed. Many babies squirm, grunt, snort, wimper, and make many other variations of normal noises.
Some very well intentioned parents may rush in and soothe them when they make these noises, but they may be actually awakening them, and starting bad habits of very frequent awakenings at night. Of course you will want to be a very attentive parent, but you may want to wait a bit to see if they are really awake. If they are, you will figure it out easily. They have good signals. 🙂 A video monitor can be very helpful to see what is really happening.