I am not a doctor, but I would guess most likely it is not “normal” but could certainly be something benign and common. I’ve had a heart murmur since I was a baby, which is a small problem with a valve. I also have an arrythmia, that I became aware of as an adult, but most likely has been there since I was born. Both of my conditions are considered bengin and do not affect my life or abilities in any way. Possibly yhte heart is not actually missing a beat, but it is just how you perceive it. Good to check it out though.