Why does my heart start skipping and having short fast runs continuously when i lay on my right side? its always when i lay on my right side. why does laying on my right trigger it? it only stops when i sit up

Palpitations: Being aware of your heart beat often occurs when you lie down on your side due to changes in your heart position. If you are having runs of fast heart beat, it's best to get yourself checked by your doctor, who may do an EKG or a heart beat monitoring test (EG, Holter monitor). One benign condition that can cause this is mitral valve prolapse.