My heart would do the same thing during a panic attack out of the blue. Sometimes, it would come in cycles like 3 or 4 times in a day and I have woke up from sleep like that as well too. Try to avoid caffeine and cold medicine and make sure you are hydrated. Also, if you bear down, your heart will slow down. What I mean by that is, when your heart starts to race like that, squat and bear down like you have to go to the bathroom. It's called the valsalva maneuver and it works. Look it up on the internet. It will slow your heart down. Take peace in knowing that nothing is medically wrong with you, it is just your fight and flight response for whatever reason kicking into high gear. I have been to the ER many times because of it and they finally put me on klonopin. I took that a couple of years and never had the problem again. But anxiety has been knocking at my door since the holidays so I am back on medicine again. If you think you need medicine, then by all means go to your doctor. There is no reason to suffer.