I'm a 17 year old female and I don't really know if I should be worried about this or not. Last year early in the morning while I was sitting down and got up, my heart starting to beat really hard and I talked to the nurse and she told me it was probably because I got up too fast and excited myself, but ever since then it's started occurring more often. Maybe once a month or two and the whole thing lasts like 2 to 4 minutes and then my heart slowly goes back to normal. I don't know if I should be really worried because it goes back to normal very soon and doesn't happen too often, but it's so unpredictably. I can be sitting, standing, laying in bed, or anything, so I don't think I'm exciting myself.