I saw this posted before, but I am too lazy to go & look for the other post. My 1 year old has recently started rocking herself to go to sleep. She does it so hard though, and if I don't move her playpen out, she'll just hit her head on the couch or wall or whatever. & she does it in the middle of the night in her bed too. Is this normal & will she stop it soon??? I don't mind her rocking herself for comfort, but it's loud when she does it in the midle of the night!!

By Sunny on Thursday, November 13, 2003 - 02:00 pm:

Found this:

Why it happens
Body rocking and head-banging are normal behaviors in babies, who seem to find the rhythmic back-and-forth movements a soothing way to fall asleep. Body rocking starts, on average, at about 6 months and may be accompanied by head-banging or head-rolling a few months later. Some babies move back and forth on all fours, while others rock sitting up.


What you can do about it
It's best to take a low-key approach to this issue. If your baby perceives that you're trying to stop the rocking, he may take it as a challenge and will persist in the behavior. Rocking in babies generally isn't a sign of any behavioral or emotional problem, and you don't need to take any precautionary steps for your baby's sake. If your baby's rocking is unusually loud or vigorous, try moving his crib away from the wall. Also be sure to tighten the screws and bolts on his crib regularly.

And this:

Head Banging, Body Rocking, and Thumb-sucking
Parents are often concerned when they notice their young children performing repeated rhythmic behaviors, such as body rocking. Fears of autism or developmental problems can haunt parents. A study published in the January 2002 issue of the Journal of the American Academy of Child and Adolescent Psychiatry suggests that these behaviors can be a useful part of normal development. In the study, children were assessed at age 13 months. The degree of rhythmic behaviors did not differ between those at high risk for developmental problems and healthy children of the same age. Behaviors that are concerning when displayed intensely by older children and adults can be quite normal in healthy young children.

Found this too, but I think it's more for older kids???

Rhythmic Disorders
Rhythmic disorders, such as head-banging, head-rocking, and body-rocking, involve movements that range from mild to seizure-like thrashing. Other rhythmic disorders include shuttling (rocking back and forth on hands and knees) and folding (raising the torso and knees simultaneously).

During the rhythmic movements, the child may moan or hum. These movements seem to occur during the transition between wakefulness and sleep or from one stage of sleep to another.

There is no known cause for this type of disorder, but medical or psychological problems are rarely associated with it. Children who experience rhythmic disorders may have morning headaches, nasal problems, and ear infections.