I get heart palps, flutters and racing heart beat randomly at times even when i am resting. Also exercise can trigger them symptoms too, i could be playing football and my heart is beating fast as you expect it to but then randomly i get this even faster heart best where it takes me back and scares me with a few flutters then after a minute it will relax and go back to a normal fast heart rate. I have asthma too so many be over using my inhalers could be a cause too not sure. I have had numerous ecgs but that’s the only test i have had and it’s come back fine. I noticed this really fast heart beat playing football since i was like 17. I think it could be what i described above but not sure.