heart palps may be a symptom of hypo thyroid. I had this big time before iodine. Your body temperature will reveal this.
Also could be a lack of or imbalance of electrolytes like potassium / sodium or magnesium / calcium, like mentioned. Very often happens with medications, especially psych meds. (thats why they often get the typical "stuffed" face appearance.)
Adressing deficiencies before further complaints about iodine, is my recommendation.