My Son, Age 30, Has A Pulse Rate Of 84

My son, age 30, has a pulse rate of 84 when normally his resting rate is 60. He is anxious, can't calm down, was shaky but that has improved. His blood pressure was erratic; first low then high.His temp was slightly low: 96.8. Gave him orange juice, thinking his blood sugar might be low, although he has no history of this. He is slender and in good health, does not use any medication. He works out daily. What could this be?