For me, when WILDing a transition is very clear. Going from consciousness to a dream has always involved some sort of physical sensation (falling, a sound that bellows so loudly you can feel it, floating and vibrations are a few I've experienced) and out of 9 transitions I've only had one where I didn't realize I transitioned. They are usually very distinct and unmistakable.

In the beginning I thought that my transitions were based off how I was laying in bed, but now that I've experienced a handful I know they vary drastically and really there is no set feeling or way to predict what will happen during your own transition.

Based off my personal experience the best way to feel a transition is wait for imagery. My mind is always filled with thoughts up until imagery, then once I notice it I clear my mind and try to fall asleep. Usually I will transition into a dream before consciously falling asleep.

Good luck