Internal white noise when falling sleep

Hi, guys!

Today I did a WBTB: I stayed awake for 2 hours and got back to bed for 2 hours. At the first 20min back to bed I felt I was falling asleep and I heard a typical white noise on my ears that starts low and continues getting higher until it stops. I try not to move and only let the noise take me, but it always stops and sometimes I wake up, but today I just couldn’t move. After one minute I could see my right hand and I was lucid, but could only move this hand and then I wake up.

Later when I fell sleep again I had a lucid dream I will write here later.

Do you have some tips or explanation for this situation?