The first time it happened was very frightening for me. It felt like I was buried alive and was not able to move.
it has gotten better, now after few seconds I realise it is happening and I just have to wait for some time.
My first time I spent a few minutes trying with all my might to move a muscle. Any muscle. I felt like I was trying to thrash around to wake myself up but there was just no way to get a signal to any part of my body.