Who can treat my childs head banging and body rocking?

Depends. This maybe normal behavior, depending upon the age of your child, seen during temper tantrums. However, i would discuss the situation with your pediatrician to insure nothing else is underlying the behavior, especially if this is not a toddler..
Think pacifier. A lot of kids can adopt self soothing behaviors that drive parents and grandparents nuts. Head-banging and rocking are two that trouble most. I consider them like pacifiers, a necessary evil for some. The less fussing you do at the kid the less they need it to fall back on ans self soothe. It does pass as they get older and find more productive things to do.