Could simply be your lifestyle...things that will increase the heart rate naturally for some people are:
Intake of caffeine not just coffee but iced tea, consumption of any sodas with any color in them other than root beer, red wine will set it off, too much sugar, drinks such as gatorade type of products with electrolytes in them, chocolate, energy drinks are a big no no,, another biggie is not drinking enough water and i mean plain water not vitamin water,,,dehydration can make them go crazy, burning the candle at both ends is bad meaning you are taking on too much and not getting a full nite of sleep with stress tossed into the mix...those are pretty much the rules of engagement for setting off a rapid heart beat..only you know what your lifestyle and intake is.....i hope it helped....
I don't know as I'm just starting on this "journey" myself. However, I have learned we can have "events" and not even be aware of them. The only way to know if there is more going on than we are aware of is a 30 day Event Monitor. A 24 hour Holter monitor very seldom gives up any information for those of us w/such infrequent "events" When your "events" are still just every 2-3 months it may be jumping the gun to consider an Event Monitor yet - but it is worth discussing these "events" w/your doctor. My events were occurring about once a month so I didn't have much confidence that the 30 day Event Monitor would catch an episode. But it did. My "events" have been increasing in frequency.