Coqueteándole comes from the verb coquetear, meaning "to flirt". The -le ending indicates that the action is being done to someone or something.
In the song, Arjona sings, "Ya te vi en el celular, en tus fotos de Instagram, coqueteándole a un espejo." He's describing seeing the person he's interested in on Instagram, flirting with a mirror. It's an interesting and slightly playful word choice that paints a vivid picture of vanity and self-admiration, making it memorable and engaging.
Ricardo Arjona plays the swaggering charmer, and the hook says it outright: 'Porque puedo estoy aquí' [Because I can, I'm here] — not fishing for a maybe. He needles the type still holding out for a hero: 'la que busca un Superman / termina con un pendejo' [the one looking for a Superman ends up with a fool], then turns the joke on himself, pricing his own attention low: 'Estoy de oferta para ti' [I'm on sale for you]. Between a cellophane-wrapped love note and a streetlamp meetup, the song stays cocky and a little crude, never sincere for long.