Enloqueciendo is the present progressive form of the verb enloquecer, which means "to go crazy" or "to drive someone crazy". It comes from the root word loco (crazy).
In the song, Enrique Iglesias sings, "Ese fuego por dentro me va enloqueciendo" (That fire inside is driving me crazy). He uses this powerful, dramatic word to describe the intense, all-consuming passion and desire he feels, which is a central theme of this energetic dance track.
This song is about that instant, overwhelming attraction you feel for someone on the dance floor. Enrique Iglesias describes a connection so powerful it's physical. He sings, "Yo te miro y se me corta la respiración" (I look at you and my breathing stops), and when the person looks back, "se me sube el corazón" (my heart races). The whole vibe is about wanting the night to never end, with their bodies "llenando el vacío" (filling the emptiness) as they dance.
The song is basically a direct request for a wild night together. The chorus is a simple, repeated plea: "Yo quiero estar contigo, vivir contigo, bailar contigo, tener contigo una noche loca" (I want to be with you, live with you, dance with you, have a crazy night with you). He's not subtle about it, listing their "física y tu química, también tu anatomía" (physics and your chemistry, also your anatomy) as reasons he's losing his mind. It's a song about pure, unfiltered desire in the heat of the moment.