Perineum waves without aneros ?

Has any of you ever experienced this ?

Yes. It's like a muscle memory. The process of waves (contractions) can be invoked by slight movement, and continue by it's own.
I have this too (but mostly in few hours after sessions)

I have also experienced it.

This happens to me all the time

Happens to me as well, although it's hard for me to tell exactly where they originate from. They just seem to spread randomly through the body. I can pretty much cause them to happen at anytime by caressing myself almost anywhere on my body. If I am relaxed when it happens (like laying down in my bed) then sometimes they can get quite intense and cause my whole body to shake a bit.

By the way I've never used an Aneros or have had any other object up my butt (except my finger two or three times). I wonder how close I am of having an orgasm, hmm.