Palpitar means 'to beat' or 'to throb', specifically referring to a heart or pulse. While 'latir' is a common verb for a heart beating, palpitar often carries a more intense, noticeable, or even anxious sensation, making it more evocative.
In "Noche De Relajo," the lyrics say, "Tú me haces que mi corazón empiece a palpitar" (You make my heart start to beat/throb). This beautifully captures the feeling of excitement and strong emotion the singer experiences when thinking about or being with this person, making it a memorable and romantic expression.
"Noche De Relajo" kicks off right when the party gets rolling. Ivan Cornejo sets the scene with "Va llegando el seis seis cuatro" [The 664 is arriving], dropping the area code for Tijuana (664) to ground the night before he dives in with his friends (compas). Soon enough, drinks flow and the mood shifts. He admits "su mente va despegando" [his mind is taking off] while music from Esteban plays in the background. The track pulls you straight into that woozy party state where time moves fast, but you feel stuck in slow motion.
Then he spots someone who completely freezes him in his tracks. He describes himself as "Tumbado y hasta enfiestado" [Laid-back, spaced out, and partying hard], totally glued to the chair: "Atrapado en la silla no me puedo levantar" [Trapped in the chair, I can't get up]. It is a funny, very real mix of being too dazed to walk while your chest is racing ("Tú me haces que mi corazón empiece a palpitar" [You make my heart start pounding]). He cannot stop staring at her lips, yet he is so buzzed and tongue-tied he blurts out "Ni sé cómo saludar" [I don't even know how to say hello]. It is the ultimate late-night crush confession, told from the perspective of someone who wants to dance but cannot even stand up.