Whether you believe all hypnosis is self hypnosis or not; knowing when you are being hypnotized is like a fish knowing it’s in water.
You are being hypnotized all the time! Every single moment of your life! And finding out who’s triggering the trances is as difficult a question as it’s answer is simple.
You know you are being hypnotized by accepting the suggestion that you are always being hypnotized.
It does not necessarily feel like anything to be hypnotized because you do it all the time!