It can be due to acid-base imbalance in the body, low sodium, calcium and vit D deficiency, Alzheimer’s disease, muscle fasciculation syndrome(a disorder of the nervous system characterized by the uncontrolled twitching (fasciculation) of muscle groups in various parts of the body),Motor neuron disease or parasthesia skin.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.