In reality, when you find yourself entering trance, it's more like when you drift off into a daydream maybe you'll even be talking to someone and whereas at first you would be aware of everything around you like the feeling of your feet on the floor and the warmth of your hands on the surface they were rested, instead you would start noticing the movement or shadows on the person's face and quickly you would start to become completely detached from your awareness.
Even if you find what the person is saying very intruiging, sometimes you're mind just seems to want to float away.
When you become completely immersed in a TV show or book, and sometimes even driving, you are allowing yourself to enter trance, you start breathing deeply and your pupils dilate and as you start to become completely absorbed and focussed, you begin to get more and more relaxed.
And that's basically what trance is, it's not like comatose, and you're subconscious mind will take you only as far as your comfortable with going. When you first begin to enter trance, it's similar to when you need sleep and you are extremely drowsy and sleepy and you try to read a book or some other focussed task, then your eyes begin to get heavy and before you realize, they begin to close as the dreaming part of your mind rises to surface and the more you try and stay awake and focussed the more the eyes begin to pull themselves down.... like heavy shutters.
And then, you fall deeply asleep