Hi i've been having this problem for a while now, sometimes my heart will flutter for a few seconds what causes this?

Arrhythmias: Your heart can sometimes have irregular beats. If this bothers you, or you have any other symptoms along with it, you should definitely see your doctor to get an ECG or wear an event monitor. That's really the only way you'll know if these feelings are dangerous or not. Hope this helps!

Palpitation: It may not be something really bad... but it is prudent to get an opinion from heart doctor. Young people could have an arrhythmia that can be life threatening. If the ECG and heart evaluation is normal, then I would advice to cut the caffeine if you take it and do regular exercise.