I'm 21 and cycle about 5 miles every day and my heart beat just pounds awat at night stopping me from sleeping. It's not painful, it's just incredibly uncomfortable - I find myself sort of contracting my muscles when it's about to beat. I also have asthma and constant allergies to dust/pollen/animal hair - could this have anything to do with it?
Or, perhaps it's because I worry a lot when getting to bed and because I'm not moving and everything is quiet, I just start automatically being aware of it? Boom boom boom buboom buboom buboom :-(