Greetings madam. It seems that you have noticed a normal physiological event that occur in every individual. You can have hot flashes while lying down because your body is adjusting to a sudden change in temperature, most likely due to your nightly relaxing routine, which usually initially brings your body temperature lower. As you get ready for bed and put on warmer clothing and cover yourself with blankets, you are increasing your body s temperature and blood flow to the brain. To regulate your core body temperature, your blood vessels dilate to release heat. The amount of estrogen( a hormone) your body is producing may be directly linked to how your body regulates its thermal regulatory center. During menopause, your body has a lower degree of tolerance before it begins regulating core temperature. This means that instead of having a leeway of a few degrees, your skin blood vessels begin dilating at only .8 degrees C change. -I Suggest you By adjusting your room temperature just a few degrees lower at night, you can usually control the nightly hot flashes you experience while lying down in bed, also lowers the frequency and severity of hot flashes experienced during menopause. Hysterectomy done individuals also experience the same. -In spite of all above measure, If you still experience the same discomfort, I advise to contact your nearby General Physician who may guide you to overcome such problem.