1. It is sunnah to grow the hair of the head (i.e. not shave off the hair of the head). However, if one is afraid that he will not be able to care of his hair, then he may shave his head.
عن جابر قال أتانا رسول الله صلى الله عليه وسلم زائرا في منزلنا فرأى رجلا شعثا فقال أما كان يجد هذا ما يسكن به رأسه ورأى رجلا عليه ثياب وسخة فقال أما كان يجد هذا ما يغسل به ثيابه (مسند أحمد رقم 14850)
Hazrat Jaabir (Radhiyallahu Anhu) reports that on one occasion Rasulullah (Sallallahu Alaihi Wasallam) came to visit us at our home. He saw a man with dishevelled and unkempt hair and said: “Does this person not have anything with which he can keep his hair tidy?” And he saw a person with dirty clothing, and said: “Does this person not have anything with which he can wash his clothing?”
عن عائشة قالت كان شعر رسول الله صلى الله عليه وسلم فوق الوفرة ودون الجمة (ابو داود رقم 4189)
Hadhrat Aaisha (Radhiyallahu Anha) reports that the hair of Rasulullah (Sallallahu Alaihi Wasallam) was longer than a wafrah (hair that reached the ear lobes) and shorter than a jummah (hair that reaches the shoulders) (i.e. his mubaarak hair was in between his ear-lobes and his shoulders).