This is a song about being so into someone that it is a little embarrassing, and Sofía Reyes owns it. The hook is right there in the title: "Estás en mi cabeza, 24/7" [you're in my head, 24/7]. She opens with "Nunca me había pasado sentirme viva tan de repente" [it had never happened to me, feeling alive so suddenly], and admits she has been in love before, "pero contigo es diferente" [but with you it's different].
The best bits are the small, cheeky lines. "Apriétame tantito, tantito más" [squeeze me a little, a little more] uses tantito, a very Mexican diminutive of tanto, meaning "just a tiny bit". Then she promises "Te juro, te prometo que no muerdo" [I swear, I promise I don't bite]. And "Si me preguntaran, te escojo más de un millón de veces" [if they asked me, I'd pick you more than a million times] is pure over-the-top sweetness. Notice "Me pongo bien sentimental" [I get really sentimental]: in Mexican Spanish bien before an adjective just means "very". It is a sunny, simple love song, and it knows it.