A 35-year-old male has experienced episodic headaches, palpitations, and sweating over the past year, with symptoms resolving within 30-60 minutes. During this episode, examination revealed: heart rate 85 bpm, BP 195/120 mmHg, no significant cardiopulmonary abnormalities, positive urine glucose, and positive urine catecholamines. After 1 hour of observation, BP and heart rate normalized. The most likely diagnosis is: