My mother goes to bed sometimes and gets the constant shakes and chills. It sometimes takes her hours to get to sleep and on occasions, we have had to take her to hospital as a result. Her heart races on and off at times whilst experiencing these chills. She suffers from anxiety however this appears to come out of no where and most frequently occurs when she goes to bed. I am wondering what physiological basis there is to elicit this sort of response? (ie: High blood pressure? Any hormonal reasons?).