If you frequently awaken in the morning with a headache you may want to consider being tested for Obstructive Sleep Apnea. During the night as a result of the obstructions, your oxygen saturation can become decreased. This results in the headache from the oxygen desaturation.
Facial muscle spasm is another common cause to morning headaches. During airway obstruction, the mouth clenches as you gasp for air. Often this causes excessive force on the jaw and temporal muscles. The result is sharp pain in the temporal and frontal regions of the head. Patients that have a preexisting history of "TMJ" are at risk for this condition.