More curious than worried....

Hello,

I am going to my first checkup in about two years. I'm a 27-year-old male, nonsmoker, low-stress career, drink alcohol occasionally (5 drinks a week at the most, usually none) though used to drink much more, exercise regularly (including a lot of walking, some biking, and weightlifting), eat well, recently lost 15-20 pounds, and now not overweight. No health problems, except pinched nerve/back problems that come and go, and no history of heart problems in my family.

Every six months or so, I have a weird sensation in my heart, like an extra heartbeat or two, or a heartbeat flutter. No other symptoms come with it: no chest pain, no dizziness, no fatigue, no shortness of breath, etc. They've occurred at random, i.e. not during exercise or exertion, not after drinking coffee, etc. I feel the "flutter" for one second, and that's it. Absolutely no other symptoms before, during, or afterwards.

I'm just curious as to what these might be; they're so minor and few and far between that I forget about them. But I had one today, and thought I should mention it to the doctor. Any thoughts as to what this may be? Is it usual for adults to have this kind of thing now and then? Thanks in advance.