Complex sentence: He described himself in his childhood years as a "loner" who preferred reading to socializing and first took up playing music when his parents bought him a guitar as a gift when he was in the fifth or sixth grade.
Split into simpler sentences: He described himself in his childhood years as a "loner" who preferred reading to socializing. He first took up playing music when his parents bought him a guitar as a gift when he was in the fifth or sixth grade.