It's just HH, or hypnagogic hallucinations; these things are known to occur as your progress through N1 sleep.

Now, the term SP is tossed around here a lot, typically in reference to the experiences a person can have as they make a WILD attempt. Contrary to popular belief, you aren't actually going to be paralyzed until you hit REM and REM atonia kicks in.

By the time you hit REM, however, you should already have made the transition into the dream. As such, expecting your body to become completely paralyzed when you make a standard WILD attempt is an absolutely silly idea that's the direct result of the perpetuation of misinformation and confusing terms by the majority of the LDing community.

tl;dr Don't expect to be paralyzed when you experience HH. You've been misinformed.