As an attempt to answer OP's question more directly, I'll post the following snippet from an SPD description I identify with (somewhat) strongly:
The Schizoid is most notably an isolated, self-sufficient type. His relationship situation can vary on a spectrum from having relations with family and friends to one that lacks any social contact. The Schizoid is introverted and more comfortable with solitary activities. He spends his mental time with an active fantasy life as a substitute for contact. He appears detached and unemotional about most of his personal issues and can seem cold and disinterested. Beneath this appearance, the Schizoid is sensitive and has deep longing to belong but may not appear that way on the surface. He has suffered pain in his life and therefore is frightened to move too close and get hurt again. So he may appear aloof.
The schizoid developmental attachment rupture occurs after the practicing sub-phase and before rapprochement in the separation-individuation stage when good and bad feeling states are congealed. The Schizoid learned to retreat and fears closeness as unsafe. This type can have distorted reality perceptions including paranoia, and lack the ability to tolerate frustration. They keep a distance to create a safe position that is maintained by self-sufficiency. They can appear standoffish and arrogant but that attitude serves to maintain safe distance rather than a superior defensive stance.
Comments regarding their outermost defenses of self-sufficiency are helpful as well as noting their fear of being engulfed and co-opted. Those observations help direct the Schizoid to his deeper feelings of profound alienation and isolation, or his anger about feelings of engulfment in the other. The higher functioning Schizoid, like Hank, longs for intimacy but is frightened to get close to another. The more impaired types steer clear of longing for friendship and relationship.
Full article here: https://orgonomictherapy.com/2015/12...r-of-the-self/.
Do any other SLIs resonate with this description?