If you have avoidant personality disorder you are afraid to speak up due to the fear of saying the wrong thing. You are uncomfortable in social situations.

An avoidant personality disorder is a disorder characterized by an irrational fear of rejection and anxiety in social situations.

could be depression, Avoidant Personality Disorder, Antisocial Personality Disorder, Schizoid Personality Disorder, Major Depressive Disorder, paranoid Personality Disorder, etc. . .

People don't acquire it, it is a genetic disorder that cannot be avoided or prevented.

People with AvPD (Avoidant Personality Disorder) display a pattern of social inhibition, feelings of inadequacy, extreme sensitivity to negative evaluation, and avoidance of social interaction. AvPD is also called Anxious Personality Disorder and it is Cluster C personality disorder recognized in the Diagnostic and Statistical Manual of Mental Disorders handbook.