Why Do I Feel Low-frequency Vibrations In The Back Of My Head And Neck When Fasting Or On A Low-calorie, Low-fat Diet?

Whenever i go on a low calorie low fat diet, or Fast for 12 hours or more, i get these weird vibrations. I can t locate them exactly but they are somewhere in the back of my head/back neck. The vibration is similar to a shaving machine on very low. I never had this issue before when i go on a diet.