Multiple Palpitations In A Row

I've never experienced this so I'm wondering if anyone else has. About 15 minutes after a workout of lifting weights I was at the gas station paying for milk when I started having heart palpitations. I'm not a stranger to palpitations and when I have them it's usually one at a time. This time it felt my heart was stuck in gear. I felt a flutter but then it felt like it was fluttering for five seconds or so and then had a thud at the end. As soon as it happened I just stopped what I was doing. The cashier had to remind me to insert my card. Has anybody had palpitations like this? Multiple flutters in a row that last more than a few seconds?

On the rare occasions I get skipped beats (once every six months maybe), when they do happen I often get them for several seconds at a time, culminating in a thud.

I find it's often when I have a bout of reflux, even if it's not immediately obvious.