Did anyone ever find out what was causing this? Internal shaking? I have been having it for years. Now my granddaughter is having it and I notice I can feel it through her skin, so I know it's a real thing and now probably inherited. I don't believe it's related to 'gas', since we don't suffer from this, but have been studying 'lectins' and believe it could have something to do with ingestion of foods that cause blood agglutination and then when you are supine somehow that effects your heart? Because mine inevitably causes a tachycardia about the time that I reach REM at night, probably when my body temperature changes. I have worn a watch monitor to try to figure it out and know from a Kardia monitor that it's tachycardia. I have had a transverse myelitis in 2015 from a quadrivalent flu vaccine, so it was interesting that someone mentioned that. I believe that could be a contributing factor. I believe lectins exacerbate that. And give you GI problems. Dr. Gunderson has written some good books about how to have a diet that helps this GI & cardiac problem. I made a chart that works for me and post it to my twitter. I've tried to eliminate most lectins. If anyone has figure it out, please let me know, or if you've found anything to take that helps please let me know, my doctor has run out of things to check for! We're talking about DNA for hypokalaemia and RYR1. I have had a reaction to low potassium with sulpha which stopped when I began taking Diltiazem. But the shaking and tachycardia remains and disrupts sleep.This is much more info than I intended to share, but am just trying to get to the bottom of this internal shaking heart problem. It's like a vibration. It's not in your head. There has to be a physiologic reason, because I can feel it in my granddaughter and she's not making it up.