Body Shy (3.5e Flaw)
From D&D Wiki
Your character doesn't like being exposed or seen.
Effect: When your character is within 20ft of any non ally, and is not benefiting from concealment or from total concealment they become shaken.
Roleplaying Ideas: I wonder if your character is an aberrant of some kind. Maybe your character has traumatic experience forcing them to be ashamed of their body.