Ok now that I have your attention, I'm wondering if this happens to anyone else and why.

This happens often enough while I'm going to sleep/relaxing, especially at the beginning of the night or if I take a nap.
I lie down in my bed on my back and relax deeply. After awhile of feeling my body sinking and perhaps losing its feeling or becoming numb, suddenly my breath quickens and my heart starts pounding and my face flushes. After that sort of dies down, I feel fully awake again as if I had just gone for a brisk walk.

This doesn't happen because I think of something or worrying or anxiety; I am perfectly calm and it just happens by itself.

So has this happened to you, and do you know why it happens?