I know they are distracting and uncomfortable but the worst thing you can do is hyper focus on them. Try to refrain from counting them. It isn't until you reach well over 10,00 or even 20,00 that doctors get concerned. I try to just see them as extra heart beats. Your heart can handle it just fine. Anxiety is a big trigger but not the only one. Caffeine, sugar and carbohydrates, chocolate and spicy foods. Anything that causes acid reflux and eating meals that are too large. Becoming dehydrated as well and working out without having eaten or not doing a proper warm up and cool down. Your heart has been evaluated to be healthy. I know it is hard to not obsess over them so maybe consider speaking with a therapist for a few sessions to learn how to redirect your thoughts away from your heart. The less attention you give the premature beats the less power they will have at hijacking your life and happiness. You are not in danger if your heart is healthy. Maintain a heart healthy lifestyle and odds are you will die peacefully in your sleep of old age. Take care.