Unfortunately I can't say for certain what you have. You have to get it captured on a monitor to know for sure. It could have been a run of premature beats which would be called PAT if it was pacs or VT if it was pvcs. Runs of pacs feel like a flutter to me, they feel fast. Runs of pvcs felt more like thumps in the lower part of my heart not quite as fast. Though I can't say for certain that is what everyone would feel. They say if you are able to cough and stop them it more likely would be a run of pacs. In an otherwise healthy heart and since you were able to stop what was happening on your own, whatever it was, it likely isn't a danger to you. It is only when a run of pvcs gets caught in a reentry circuit that they pose a threat. It doesn't seem like that was the case.
The other thing it could have possibly been was accessory pathway svt. I had that as well. A version called avnrt. I would get a premature beat and then all of a sudden my heart would race at speeds well into the 200s and then go back to normal just as suddenly. The heart beat felt normal but crazy manic fast. It would be hard to breath and cause me to feel like I would black out. You need a monitor to catch it so maybe see if you can get a 30 day monitor to catch what is going on. But from what you describe odds are it is just a run of pacs but it might be good to know exactly what it is. This said, since your heart is healthy if it is a simple run of pacs or pvcs they likely won't do much for them except prescribe beta blockers. There isn't much that can be done about them unless they reach the 20,000 mark or get caught in a loop that we can't stop. So keep coughing when you notice them and avoid the big triggers, caffeine, sugar, carbohydrates, heavy big meals, spicy meals. Address acid reflux and work on stress and anxiety. Then just try to drink lots of water and do proper warm ups and cools downs when exercising and hopefully that will keep them from bothering you too much. If you are super bothered by any of it or it starts to disrupt your life a lot then just go back to the doctor to see if you can catch what it is.
As for it happening in a normal heart there really is no such thing as a normal heart. They say the vast majority of us will experience premature beats but some never notice them. Anxiety produces chemicals and adrenaline that cause us to feel things more acutely. They raise the heart beat in preparation for fight or flight and as such can cause the heart to get over stimulated thus triggering the premature beats so unfortunately anxiety can be a big trigger. It is for me. That and acid reflux and chocolate are my big triggers but I'm not giving up chocolate so my heart will have to deal with a few hours of premature beats as a result lol. My svt I had corrected by ablation but the premature beats I just have to live with. If you have svt they can correct it but otherwise just try to take the premature beats in stride. The less importance you give them the less they will bother you. Mind over matter as they say. Take care.