I didn’t consider that I am on the spectrum until my son and then wife told me I could be. That started my investigation. I also don’t have obvious outward characteristics, but I’ve been hiding it since I was in 3rd grade. Lots of things on my head and concealed.
https://embrace-autism.com/autism-tests/
Start here and see where this takes you. This is what I did. I’m older and don’t see a reason for a full eval. I’ve also been reading and searching to see if some things I do are autistic. If you aren’t sure, start here, or find some other online tests.