I never "had" it either untill I started paying attention.

HI, or HH are images or "videos" we see as we are falling asleep. They can also bee sensations or sounds. If we don't pay attention and don't have intent to see them, then our mind falls asleep pretty much at the same time as the body.

When we are WILDing, we are purposely keeping our mind awake while our body is falling asleep. That's when we can see, hear or feel HH.

When you are experiencing HH, do some motionless RCs. Try to move your arm, sit up, stand up, roll off you bed, levitate up just by thinking about it. If you move, you will know you are in a dream already and what moved is your dream/astral body. You are lucid and you can walk away to have some adventures.