I agree with above. I have bad palpitations but nothing like what you have described.
My guess would be electrolytes as well - loss of sodium potassium? Magnesium and Calcium ie Paramin are meant to really slow your system down and Magnesium is known to calm your heart. That being said monitor closely because the heart is not an organ we want to ignore when it tells us something. Couldn't hurt to see a gp if it continues.