Trembling sensations are usually related to fears. Fears can be related to anxiety disorders. Other causes include high fever. Example of fears could be social anxiety disorder.
 

The unifying theme in social anxiety disorder is a fear of performing poorly in social situations and suffering from embarrassment or humiliation. By definition, social situations mean interacting with or performing for other people and being under their potential scrutiny. If a socially anxious individual's performance is found wanting in some way, he often says to himself, "How embarrassing" or "How humiliating." This fear of embarrassment or humiliation causes these individuals to either avoid those situations altogether, or suffer extreme anxiety as they endure them. Their lives can be further complicated by anticipatory fear of upcoming social encounters.

In addition, social anxiety disorder sufferers often experience physical symptoms before or during social interaction. They may have palpitations, sweating and trembling. Some experience flushing or blushing. These physical indicators of anxiety may become part of a vicious cycle. As socially anxious individuals anticipate or become involved in social encounters, they experience an increase in these troublesome symptoms, which makes them even more anxious. In addition, they worry that their anxiety or awkwardness will become even more obvious, and this, in turn, leads to further embarrassment and humiliation.

• Fears
• Phobias
• High Fever

This depends on specific conditions. Ask your doctor if not sure.

• If you feel chest discomfort during these moments of fear.

Your doctor will perform a physical exam, and determine what is causing your perspiration.