Excerpt: "Persons with stereotypic movement disorder move their bodies in ways that are nonfunctional, repetitive, and seemingly driven. This may include relatively benign movements such as rocking, hand waving, and twirling objects. However, it may also involve dangerous or even life-threatening behaviors such as head banging and self-biting."
Thurston, Nancy S., "Stereotypic Movement Disorder" (1999). Faculty Publications - Grad School of Clinical Psychology. 287.