You need to see your Doc and have an ECG done. If it's a random occurrence they'll send you home w/a portable ECG (Holter Monitor) to wear to record so they can see what it's doing when it happens.
Sounds like Paroxysmal supraventricular tachycardia (PSVT)
How long do the episodes last?
Well, this may freak someone out, but they never stop actually. Whenever I check my pulse it's irregular.
The strange thing is I can sleep fine, there's no dizziness, shortness of breath or chest pain (PSVT symptoms).
Should I avoid working out until I get it checked out? Because I do experience shortness of breath during my workouts, which I believe is normal but you never know.