Hola Martin, llamar la atención -> to attract attention (atraer) lo que más me llamó la atención fue… -> what struck me most was… al principio no me llamó la atención -> at first I didn't notice anything unusual

1) This is what caught my attention. 2) it catches my attention

'my attention' means my awareness, of something or someone. examples: "it came to my attention that you were late this morning" = i know you were late this morning. "can I have your attention please" = can you look & listen please.