https://www.nimh.nih.gov/health/publications/panic-disorder-when-fear-overwhelms

Do you sometimes have sudden attacks of anxiety and overwhelming fear that last for several minutes? Maybe your heart pounds, you sweat, and you feel like you can’t breathe or think clearly. Do these attacks occur at unpredictable times with no apparent trigger, causing you to worry about the possibility of having another one at any time?

https://www.samhsa.gov/mental-health/anxiety-disorders#panic-disorder

Panic disorder involves frequent and unexpected panic attacks – sudden periods of intense discomfort, fear, or sense of losing control, even when there is no clear danger that typically come without warning. These panic attacks can occur as frequently as several times a day or as rarely as a few times a year.

People who experience occasional panic attacks may not develop panic disorder. Instead, those with panic disorder have repeated occurrences of panic attacks. They often worry about when the next attack will happen, to the point where they will avoid places and situations that they know have affected them in the past.

https://mhanational.org/conditions/panic-disorder

Panic disorder is characterized by unexpected and repeated episodes of intense fear accompanied by physical symptoms that may include chest pain, heart palpitations, shortness of breath, dizziness, or abdominal distress. These sensations often mimic symptoms of a heart attack or other life-threatening medical conditions. As a result, the diagnosis of panic disorder is frequently not made until extensive and costly medical procedures fail to provide a correct diagnosis or relief.

Many people with panic disorder develop intense anxiety between episodes, worrying when and where the next one will strike. Fortunately, effective treatments have been developed to help people with panic disorder.