Possible overactive thyroid
Re-Heat may be right, get your blood test done for thyroid function. When I had a recent bout of hyperthyroidism my pulse rate hit the roof with close to 180bpm. Symptoms include intolerance to heat, loss of weight, high blood pressure, sporadic itchiness all over the body, frequent bowel movements and general irritability. Once this is diagnosed treatment is protracted but generally effective. Good luck