hi- JUST went to see my doctor last week about the very same thing.
it would be a good idea to go get it checked out... but most often, it's nothing to worry about- doc says these happen to lots of people throughout the day, some people are able to feel them more than others, but it's not anything to be concerned with (my heart is perfect, btw... thankfully!).
just to be safe, have a doctor run a test for you... also, keep track of triggers- caffeine, high sugar intake, etc. those are normally easy remedies.
and DON'T WORRY! stress