I woke up after about 8 hours sleep with a racing heart. For over 4 hours in has been above 100 and as high as 134. I can feel it with my skin through out my body. My Garmin HR says it has remain elevated at this rate since 6:40 am. My normal resting rate is 57. I am about 300 lbs, 65 years old and exercise regularly. I am probably low on iron right now. I am starting a head ache.