When an individual's heart races for no reason and they are hyperventilating, this is symptomatic of which disorder?

This could be a panic attack. This is when a person experiences a intense feeling of anxiety and hyperventilation for no apparent reason. This may vary by degree, some people experience this rarely, while there are other which experiences this attacks quite common. Even interfering with their daily lives.

Anxiety Disorder

When an individual suffers from anxiety disorder, he or she can become anxious, nervous, uneasy and begin hyperventilating around perceived threats, that in reality might not be dangerous at all. For instance if a person is socially anxious, he or she might start hyperventilating, feeling uneasy and very anxious during a party.