What I get sounds exactly like what roadrunner gets.  I've noticed it for a few 2-5 years.  It seems like some kind of sleep apnea, sometimes I'll have a dream that gets more intense (involving physical activity) then I wake up with my heart pumping hard.  Other times I just wake up (without anything noticeable in my dream) and my heart feels sore (and I can barely feel it beating).  After a few minutes awake it goes away.  I went to the doctor and have slept with the EKG three times and 24 hour blood pressure monitoring once.  None have shown anything significant (I sleep more lightly when wearing them), and when I wore the EKG while running it was also fine, so my heart/blood are fine when I'm awake.  I worry that my crappy bed, which forces me to sleep on my back is causing occasional apnea.  It's more likely to occur on days when I drink alcohol, and I'm wondering if days when I eat shortly before bed increases the liklihood of it happening.  Does anyone know what's going on? and how to fix it?  the cardiologist didn't find anything significant, the next step would be a sleep study, but if I barely sleep during that then it probably wouldn't occur anyway.