I just happened across a friend a few minutes ago that has had these palpitations, plus! She told me to tell you to stay away from caffeine and that some people have different triggers for pvc's and pac's...it could be something you ate...stress...exercise...she said to keep a log if possible and maybe you can find something external that's causing them and then you can avoid that. Also trying to distract yourself while they are happening may help to get your mind off them.
I hope this helps you!!