Anyone ever get false sleep paralysis or sensations?

What I like to do is practice WILD technique before I first go to bed at night. I know that I will not lucid dream the first time I fall asleep at night, but I like to practice staying still and visualizing scenes so that I'm better prepared during WBTB (and it helps me fall asleep initially). The only thing is, when I'm doing this, sometimes my body feels really heavy, or my eyelids will flicker a little, or I'll feel like I'm washing away. Only I can't be going into a lucid dream! Where are the sensations coming from? Does this mean that when I WILD after ~5 hours of sleep, I shouldn't trust those sensations as true SP and HH?

I do something like this almost every night. The most common sensations that I get while doing this is numbness and the feeling like my body is either melting or being absorbed into my mattress. I believe that you can go into SP in the beginning of the night even if it will not result in a LD.