Restless At The Same Time Every Night

My daughter is 7 weeks old and is a decent sleeper. She sleeps 9-3 and then nurses back to sleep. However, around 4AM every night she gets very restless - constantly moving her head side to side, grunting, and making all sorts of noises. She is still asleep through all of this and doesn't seem to be in pain or straining but it keeps me up because she is so loud. Any idea what this could be or what I can do about it? Or is it something she just needs to grow out of?