Introvert (3.5e Flaw)
From D&D Wiki
People-ing is hard. And tiring.
Effect: Charisma based skill checks cause fatigue for 1 hour. While fatigued introverted characters take a -2 penalty on all charisma based skill checks. Any other activity that causes fatigue normally will cause exhaustion if an introverted character is already fatigued by this flaw.
Roleplaying Ideas: Characters with this flaw may take to hiding in the back of their party, and may avoid introducing themselves to npcs.