I sometimes feel dizzy before sleep. it's not a vertigo in full sense of the word rather it feels that everything moving a bit.. what could it be?

BPPV: It could be benign paroxysmal positional vertigo. This is usually triggered by laying to the right or left side and lasts for a few seconds to minutes. There usually is brief, intense spinning during the episode. Otherwise, more details are needed. Dizziness or vertigo requires a careful, detailed history. Many factors can contribute to your condition. See an ENT to help evaluate this.