When I was a young girl, first married, and read the book (first one on Astral Travel and how to do it) by this man,
"Journeys out of the Body", I don't recall anything you mention occurring, physically.
I think the mental however, has everything to do with how you will approach this subject, and experience it.,meaning that the fear you have, is therefore, subconsciously affecting your autonomic nervous system which in return supplies the blood rushing to various parts of the body.
What do you fear, is the first question you need to ask yourself.
Fear of the unknown? IF so, then perhaps you should wait until such things like this happen naturally and of their own accord.,and not try to force it.
Why do you force it anyway?.........IF just for entertainment value, it may not be the best path to follow, IMO.
IF you are successful in this approach, you may end up in realms, dimensions of mind, that you can then entertain yourself, with; but what good is this for the soul's value??
This is how I see it anyway.
For my husband, he use to do this nightly, but, wasn't trying to separate, (the mind from the body) purposefully, it just happened to him "naturally", ever since he was a small child.
Therefore when we married, and this started up again, (moaning in his sleep, as the separation started to take place), that is when I bought the book mentioned above.
We then had a name for what was happening to him, (Astral Travel)
or OOBE (out of body experience, they call it today)
But, he decided wisely I think to just let it occur of it's OWN device.....and occassionally, he just dreams of being out of body, Lucidly etc.
To each their own however, as I too did try, so I can't admonish anyone for doing so, as it's intriguing anyway.
But now I have no interest in trying it anymore, feeling that it's best to let the soul take over, and not my conscious mind.
The conscious mind is here on this level of awareness for a reason, and not to runaway from the pain, hardship and upsets we feel each day, by developing techiniques, (whether drugs, peyote, mushrooms, etc.), to escape from this level.
I think faith and developing faith makes much more sense.
But that's just my opinion.
Deb.

I'll post the book because now it's free online, in a PDF format next.
You might find it interesting with his proven techniques if you still want to try and do this.