Yes i've woken up many many times to my heart flying bout out my chest....sometimes it's from a night out drinking (dehydration), sometimes it's what from I ate before bed, sometimes it's a scary dream I had, and other times it's for reasons I still don't know! about
a month ago I woke up around 3am to my heart going so fast that I couldn't do anything to stop it and I called 911...they never found anything at the ER but it was very, very scary!!! I'm sure it's just dehydration and anxiety, just keep water next to the bed like I do now!
I do find that if i lay there and just relax all my muscles and do deep breathing, that helps