That's interesting, LR, I think I had that once. So - you're not alone, but I'm much less experienced at it than you!
Just to check it's the same, I "woke up" but found all limbs heavy as lead and unresponsive. My breathing was that slow, steady rythm of sleep. My eyes were open and I could see and hear, but not speak. I found it not unpleasant, and went back to 'proper' sleep. Is that the same?