What Causes Heart Palpitations?

heart suddenly stops, for about 2-3 seconds, starts again and I can feel my heartbeat so heavily, it feels like it s going to come out of my chest. I have days where this actually stops me from sleeping , my chest hurts sometimes. It feels like...my heart is losing balance, I can feel my heart now and every few beats it becomes irregular, resting heart 38 bpm under exercise 167 bp ny heart stopped 24 times for a period 2-3 sec in a 24 hour period mainly during the night