I have suffered from a more prenounced heartbeat at night - it feel like a much heavier beat, and if I start to fall asleep, it feels like a surge of sdrenaline is released and I wake up. My though it that it's aprtly due to overthinking, especially when it's quiet and I am laying in bed. Secondly I believe it is low electrolyte levels (mainly magnesium and potaasium). I found that if I eat more bananas, drink coconut water and soak my feet in epsom salts for 30 mins in the evening, it stops palpitations and overall gives a more relaxed feeling.
My sleep has been terrible recently but since introducing the electrolytes it has begun to improve.