What Causes Palpitations While Lying Down?

Hi, My name is Karen and I have been experiencing a strange thing when I lay down to go to sleep. When I go from standing to laying down my heart seems to start racing, like I m doing a physical activity. It takes a little while, maybe 15 minutes or less and then it slows down and feels better. Once in a while its bothersome enough that I get up and get something to drink or take a teaspoon of Natural Calm a powered magnesium supplement I sometimes take for my occasional restless legs. I also have been experiencing headaches 2-3 times a week. I never used to get headaches. I do get sinus pressure when the weather changes drastically (I live in Indiana) but these headaches are usually on the very top of my head. Also, even when I don t get the racing feeling I sometimes get this feeling like Water trying to go uphill I know that might sound strange but if I turn over from one side to the other side, it feels better. I always sleep on my sides, never my back or stomach. Thanks Karen