Anxiety or Panic Disorder: This is often the most common cause of heart palpitations and sweating at night, especially if the patient has a history of anxiety or panic attacks. The symptoms can be triggered by stress, fear, or other emotional factors.

Hyperthyroidism: An overactive thyroid gland can cause heart palpitations, sweating, and other symptoms such as weight loss and tremors.
Sleep Apnea: This condition can cause pauses in breathing during sleep, leading to palpitations, sweating, and other symptoms.
Hypoglycemia: Low blood sugar levels, especially at night, can cause palpitations, sweating, and other symptoms such as confusion and tremors.
Caffeine or Nicotine Withdrawal: Withdrawal from these substances can cause palpitations, sweating, and other symptoms such as anxiety and irritability.

Myocardial Infarction (Heart Attack): Although less likely, a heart attack can cause palpitations and sweating, especially if the patient has a history of heart disease or risk factors.
Pulmonary Embolism: A blood clot in the lungs can cause palpitations, sweating, and other symptoms such as shortness of breath and chest pain.
Cardiac Arrhythmias: Abnormal heart rhythms, such as atrial fibrillation or ventricular tachycardia, can cause palpitations and sweating, and can be life-threatening if not treated promptly.

Pheochromocytoma: A rare tumor of the adrenal gland that can cause palpitations, sweating, and other symptoms such as hypertension and headaches.
Carcinoid Syndrome: A rare condition caused by a tumor that produces serotonin, which can cause palpitations, sweating, and other symptoms such as flushing and diarrhea.
Thyroid Storm: A rare and life-threatening condition caused by an overactive thyroid gland, which can cause palpitations, sweating, and other symptoms such as fever and confusion.