Have you been to a doctor for these symptoms? You might want to have your thyroid levels checked. Those were exactly my symptoms a couple of years ago and I assumed they were from either anxiety or too much caffeine that day. When I went in for my yearly physical, they did blood work and found out that my thyroid was overactive. It would feel like my heart was beating out of my chest when I would be lying down relaxing or watching tv. Also, I would feel shaky just lying there in bed. It started to cause slight hand tremors in my fingers. My handwriting turned really crappy and I had no idea why.
I'm not suggesting that's whats wrong with you, but it should be something you should have your doctor check out to be on the safe side.