hi davone, welcome to health care magic, I can certainly understand your extreme suffering regarding your unpleasant experience during sleep. I can explain you that these nightmares are mainly due to imbalance between REM (Rapid Eye Movement) and NREM (Non Rapid Eye movement) stages of sleep. In general , these two stages maintain sleep balance for its homeostasis, in your case ie in nightmares, the REM activity will be too much than normal, thus the balance is lost. As this is the phase in which the brain is very active, your heart rate will be more, bacause of all these you are experiencing that kind of restlessness. you can get rid of this problem by following strict sleep hygiene ie keeping a regular wake-sleep schedule is very important,which will help to prevent the sleep deprivation that can bring on nightmares, engaging in regular exercise, which will help alleviate your nightmare if they are due to anxiety and stress,You may find yoga and meditation are also helpful. Be cautious about use of alcohol, caffeine, and nicotine, which can remain in your system for more than 12 hours and often disrupt sleep patterns. Make your bedroom a relaxing place that is reserved for sleep and sex, so that you don t associate it with stressful activities. I would like to know are you taking any medications? as certain drugs like antihypertensives may cause this effect, but very rare. Have you experienced with any severe stress (PTSD) recently? If so, consult your doctor immediately...and get back to me if u have PTSD. Please post your further questions if any Thank you