Enredar means 'to entangle' or 'to mess up'. It's a versatile verb that can describe physical tangles or more abstract emotional complications.
In this song, the singer uses it to describe how someone's thoughts began to 'enredar' (entangle) his own, even though he's trying to forget them. It beautifully captures the struggle of trying to move on when someone's memory keeps getting intertwined with your plans.
Have you ever tried to get over someone by making a super detailed plan to just not think about them? That's exactly what José Felipe Mejía is singing about in "Haciendo Planes (En Vivo)"! He's trying to convince himself that he'll kick this person out of his mind, saying "no es posible que tan solo en un instante mis pensamientos comenzarás a enredar pero mañana voy a echarte de mi mente que está planeado ya no vuelves ocupar" [it's not possible that in just an instant you started to tangle my thoughts, but tomorrow I'm going to kick you out of my mind, it's already planned, you won't occupy it again].
He's got a whole schedule: showering, watching TV news while eating lunch, avoiding couples kissing in the park, finally reading that book he never started, and even writing a new song on his guitar! He's so determined that when her smile, eyes, or lips come to mind, they just won't have a place. But here's the funny, relatable twist: after all that planning not to think about her, he realizes he's written a whole song about her! He even admits that a news story reminds him he's "bañado por salir ir a buscarte" [bathed to go out and look for you]. It's a sweet, slightly ironic look at how hard it is to truly forget someone when they've already tangled up all your thoughts.