My heart stops beating and just kinda shakes and vibrates?

sometimes my heart will just stop beating and vibrate and shake and stuff, it happens randomly sometimes, it varies from lasting like 30 seconds, to like 20-30 minutes sometimes, when its longer, it feels like im not getting enough blood to my body, and everything feels like its starting to go numb, please help me out, no one seems to know much about this when i ask them, but they all seem to think its pretty bad, so idk, help me out please