Yes, I quite often cant sleep and out of the blue my heart starts to beat really fast and I get all sweaty, and feel out of breath, when all I was doing was lying down trying to sleep. I do tend to think/worry about things, so its probably that. I saw my GP about it, and he gave me some sleeping pills, which just make me sleepy all day so i stopped using them. If you are breathing fast it could be a minor anxiety attack, best thing to do is try and calm yourself down, breathe easy, get out of bed and walk around, Ive found having a cold glass of water helps.