here is what i have found ,
What should I know about head banging, head rolling, and body rocking?
Rhythmic movements include head banging, rolling, and body rocking. Head banging is when a child repeatedly hits their head against a solid object such as a crib, as much as 80 times a minute. This can be distressing to the parents or caregivers for concern of injury. However, the child does not appear to be in pain, but rather calm and content. The habit usually begins around age nine months and resolves by around age two years. The episodes usually last from 15 minutes to a few hours, and typically occur while listening to music or falling asleep.
Head rolling is when an infant rolls their head from side to side when lying on their back. They may even rub the hair completely off the back of their head.
Body rocking is when a child rhythmically rocks while either sitting or resting on their knees or elbows. This behavior usually starts around age six months and disappears by age two. Most children rock for 15 minutes or less. Like head banging, it occurs while listening to music or falling asleep.
Head banging, head rolling and body rocking are common childhood self-comforting habits
. These behaviors are often harmless, but can be worrisome if your child also has developmental delays
. Talk about the habit with your pediatrician, who can help you decide whether there is any cause for concern.
so by the age then your child "should" of outgrown this
what is your child communication skills , are they "normal" or delayed