Lil Nas X‘s nearly naked adventure was brewing almost 15 hours before his early morning arrest … based on a new strange video of him wandering aimlessly around Hollywood!

TMZ Hip Hop obtained this surveillance footage recorded outside the Short Stories Hotel around 1:30 PM Wednesday. Sources at the hotel confirm he was there, although he was not a registered guest.

Still, the video makes it seem like he was going through something — you see Montero all by himself strolling off the street, and into the hotel’s courtyard area.

Unlike his shocking encounter with a bystander early Thursday morning, Lil Nas X was fully dressed at the Hollywood hotel — cowboy hat and boots, jeans and a short-sleeved shirt — as he fanned himself.

The “Old Town Road” rapper later found his way into the hotel’s lobby, where he hydrated with a cup of water … and then, for some reason, decided to go shirtless as he walked back on the street.

We broke the story … Lil Nas X ended up wandering Ventura Boulevard — about 7 miles from the hotel — at 4 AM Thursday, wearing only his tighty whitey underwear and white cowboy boots.