changing heartbeat at night

Changing heartbeat at night

I can hear my heartbeat in my ear. I know that the heartbeat goes up at a bit when changing sleeping position at night. My night rest gets disturbed a lot; I wake up from hearing my heartbeat changing and getting louder. In rest, at sleep I have a heartbeat around 40-50/min, but when I turn over on my other side, or even just move my legs my heartbeat gets up to 80-100/min beats (some times even higher). This last for about 10 seconds (of what I am aware) before it slows down again. Could you please tell me how much it can go up before you speak of a problem?
Thank you