I have something similar but I didn't realize that was a problem outside the relationships that were supposed to be romantic, not just plain friendships. It kinda started at age 18 or so for me? The schizoid symptom list you linked doesn't fit me though. For example I do take pleasure in sex and other activities just fine. Part of the list did fit me at age 18 though but at that time I noticed very quickly that something was wrong. I soon somehow managed to get some emotionality "reloaded" (out of sheer luck?). Until then, I could not feel at all for a while, was completely disconnected emotionally from the world and people, I didn't even get as much pleasure out of sensory stuff, felt partially disconnected in that sense too. Pretty f*cking detached overall and I stopped seeking out anything social for a while. I just withdrew from the entire world and stayed at home. I could pinpoint the triggers for that reaction but I do not understand them. Well then I slowly got - somewhat - restored to normalcy, meaning my baseline. My baseline was always somewhat detached but not to the schizoid pd degree. But yeah, even this normal baseline didn't fully get restored, only partially, and so for a long time I didn't really have close relationships on my radar at all. Then some desire did come up a couple years back...? It's all really confusing and it triggers really weird crap in me. The positive side of it is that I do lately feel like I'm getting more quality relationships developed between me and a couple friends. Still no idea about the romantic side of things, tho'.

@missatomicbomb how old are you if I may ask?