A 42-year-old female presents with recurrent episodes of waking abruptly from sleep with intense fear, tachycardia, diaphoresis, dyspnea, and chest tightness. These episodes have occurred approximately 3 times per week for the past 2 months, always during the first half of the night. She becomes fully alert within seconds of waking and can clearly recall the episodes, reporting no dream content or confusion upon awakening. She denies snoring, witnessed apneas, or excessive daytime sleepiness. Her BMI is 22 and neck circumference is normal. She has no history of seizure disorder, and her medical workup including ECG, echocardiogram, and thyroid function tests are normal. She reports developing anticipatory anxiety about going to sleep, which has led to delayed sleep onset. She has a history of daytime panic attacks diagnosed 5 years ago that resolved with treatment. What is the MOST likely diagnosis?