Sounds very similar to my experiences actually. For a long time, years I think, I used to believe that I was going to die or something when this was happening and I'd force myself awake. But I eventually got sick of it and just went with the flow to see what happens, see if I really did die or not. I'm totally used to it now and quite like it when I start to feel like this, usually struggling to stay asleep instead of waking up.