Schizoid Personality Disorder is characterized by avoidance of social situations, lack of interest in relationships, emotional coldness and a preference for solitary activities. It is diagnosed when four or more criteria are met, including not desiring close relationships, choosing solitary activities, and lacking interest in sex or close friends. Treatment focuses on improving social and coping skills through cognitive behavioral therapy and social skills training, though success is often limited due to low motivation to change. Coaching those with SPD requires patience, avoiding probing for emotions, focusing on intellectual topics, and accepting limited engagement and reciprocity.