It does indeed sound like you have an svt similar to mine, avnrt. It starts and stops in one beat for seemingly no reason. Mine were pretty short lived until I reached my 40s and then it start to disrupt my life. I had an ablation to correct the issue. Essentially there is an extra muscle fiber in your heart that allows the signal to get caught in a loop. It is an easy fix though with you being pregnant there might be an issue because you would need to be sedated to have it fixed. I believe there have been a number of women on this forum who have had svt and still had children without issue but I would go see your doctor, tell them your symptoms and you should go to a cardiologist to get evaluated. The fact that you only have it 5 times a year might make it difficult to catch. You have to catch it to get it diagnosed but it might be worth a shot. That said, if you do get it just try and stop it as soon as you can. Try holding your breath and bearing down like straining to go to the bathroom or try drinking a really cold glass of water and see if that gets it to stop. If that doesn't work then don't hesitate to go to the ER. I actually never went and I still have a fine heart but considering you are pregnant it might be safe then be sorry. But do go and get evaluated. But more than likely you will have a fine pregnancy. Take care and keep us posted on how you are.
Have you had your palps evaluated? If you have a structurally sound heart it shouldn't effect your pregnancy.I had PVC, PAC and SVT throughout mine with no problems. You certainly should be evaluated though, if for nothing else but your piece of mind. Good luck to you!