To Sleep
To Lie Down, To Go To Bed
intransitive verb, ichidan verb
ねる
寝る （ねる） To Sleep, To Lie Down, To Go To Bed
眠る （ねむる） To Sleep, To Fall Asleep
To Lie Down 寝る uses the shorter ねる reading because you just went to bed. You might still be listening to the radio while trying to fall asleep.