Anxiety about the heart can produce exactly what you are talking about: racing heartbeat after you have gone to bed. It helps some people to tell themselves, when this happens, that if indeed they have a heart attack they won't know the difference anyhow... or won't care. If a person also has racing heartbeat in daytime and trying to get over his "cardiac neurosis" doesn't help, it's time to see the doctor. It may turn out to be sinus arrythmia, which is a nuisance and may scare you but it's harmless. Also, are you on a statin? That could cause this too (rare side effect, but it happens). If you have sinus arrythmia, ask your doctor how to stop the run-ups in heart rate: there are a number of ways to do that very easily.
Hi there,I have exactly the same problem as you.My heart starts pounding for no reason day or night and my pulse gets up to 140.I found that the more i check my pulse or blood pressure the more my heart races.I think it panicks you and it then gets worse.I have found drinking lots of water gradually slows it down therefore maybe it's a bit of dehydration.