i notice that I get palpitations after driving in the car or sitting on an airplane, especially when I am travelling for more than an hour.  I first noticed that I was having palpitations when I got out of my car at work, but then had them recently after a two hour flight when I deplaned.  I tend to slouch when I sit, could my posture cause the palpitations?
Hi There In some people after a while of sitting when they stand up back they feel their heart beating fast. This happens because when we sit some amount of blood get accumulated in the legs and when we stand back up that blood returns to heart making it beat faster. I would like to suggest you to stretch your feet and legs for a couple of times before standing up. This will help to avoid palpitations. Wish you good luck