Yes, it's possible. I was diagnosed this year and I was never fully aware of masking. I remember when I went through th diagnostic criteria and was thinking "me, stimming? highly unlikely", but then I observed myself for weeks and realized I do it very often, mostly alone and in public settings under the table. Same went for losing attention, I made up games not to get bored. For example as I'm an anime fan, I learned voices from anime and also some social clues from Japanese conversations (they tend to say short words to ensure the other person they are still listening and paying attention. Something like "oh really?", "no way!", "hmm hmm"). So I started using these in my own language and.. fell in love with my own voice This way it's funny to listen to someone, even if I don't pay attention.