Hey, Im 19 but this has been happening for a long time, though its rare. Out of nowhere, my heart would beat 4-5 times really fast, when it does this it s like I get jolted and it feels really good. Nothing nasty here. I mean like.. it gives me a weird moment where I breathe in and get a bit light headed, then gives me this tinge of a good feeling. NOT talking about love or anything. I could be alone sitting down doing NOTHING and it ll jump at me. I ve been really curious about it.