I guess having DID means i have had it almost all my life, since young childhood. I thought a lot of things like hearing voices and feeling floaty and having "fairy headaches" were normal. I didn't know other kids and people didn't have this.
The things that prefaced my being diagnosed with DID, which might be more what you meant, were hearing voices, having vivid flashbacks, having time gaps revealed, panic attacks, depersonalization, and behaving in ways which were very out of character for me. All of these symptoms could also be attributed to other disorders too, which is why this can be difficult to diagnose. (I still sometimes question my diagnosis, even though it has been confirmed by various things. I can feel conflicted about it.)