Hi SS
It is quite difficult to describe these things I know, or to understand why it is happening.
It can be viewed from a 'spiritual' experience - that is why I said I would like to experience it, to know that our 'spirit' will leave our body when we die.
Or, from a 'mental illness' perspective - when you really don't want this to happen and find it frightening and traumatic. Could be side effects of meds etc.
Maybe, if the 'fear' is removed, if you felt safe and understood what was happening - it would be easier to deal with.
If you are familiar with the 'Chakra's' - energy centres? the description you gave would be relating to your solar plexus - this energy centre is our 'power' centre, also fear, anxiety, stress. trauma can be held here.
If you feel it coming on again, try the methods I suggested above. It's about being 'grounded' in the physical.
Hope that doesn't confuse you further
Warm wishes.....