I've had this experiance.
It feels really werid. You are wide awake, yet the body refuses to move in any shape or form! It reminded me alittle on when I had spinal blocks for the caesareans for my children's births, only more extreme.
You can't even physically open your eyes!
The times it has happened to me is when I simply am exhasted and need the rest, like my body is telling me it simply cannot get up and go.
The easiest way to deal with it at the time is to simply go with it and relax. An enforced meditation in a strange way.
Ensure you are getting plenty of rest and looking after yourself on all levels would be my advice.
Love and Light,
Evie