Why do i get irregular heart beats when i lie down?

Premature beats: Are you sure you only get irregular beats when you're lying down or is it that you're unaware of them when you're active? Wearing an ambulatory(holter) monitor for 24 hours would give you precise information about your heart rhythm. Avoid caffeine, nicotine, chocolate and alcohol if you're having frequent premature beats which make you feel like the heart is skipping. Check for an overactive thyroid.