Is it Sunnah to shave the head?

Shaving the head is of six types:

1. Obedience and an act of worship (Qurbah): This occurs in four instances: Hajj, Umrah, shaving the head of a male infant on the seventh day of his birth, and shaving the head of a disbeliever when he embraces Islam. 2. Shirk (Polytheism): If it is done in submission to other than Allah the Almighty, as some disciples do for their sheikhs. 3. Disliked Innovation (Bid'ah Makruhah): Such as making it a symbol for righteous people or a part of complete asceticism, as the Khawarij did, or commanding a penitent person to shave his head. 4. Forbidden (Haram): Such as shaving it upon a calamity of death, or to imitate disbelievers and transgressors. 5. Permissible (Mubah): If it is for a need, such as for medical treatment for an illness or to remove the harm of lice. 6. Disputed among scholars: This is shaving the head without a need or reason. Some scholars disliked it because it is a sign of people of innovation, while others permitted it. However, it is preferable not to shave the head except during the two rituals (Hajj and Umrah).