Unpopular opinion II: You should have your next D&D character be a teenager.
Part of the point of D&D, to me, is emulating fantasy fiction. In this genre, young and inexperienced protagonists are the rule, not the exception. Conan the Cimmerian; Eragon; Harry Potter; Lessa from Dragonriders of Pern; the Pevensie children from The Chronicle of Narnia; and Arya Stark, Danerys Targaryen, and Jon Snow from A Song of Ice and Fire are just the first few examples off the top of my head of fantasy heroes who begin their first adventures before age 18.
What's more, I would think that younger people are more likely to go out adventuring than older ones, realistically. Teenagers aren't yet tied down to careers, spouses, and children of their own. They have the freedom to leave home and throw themselves into danger- and lack the wisdom to know that they probably shouldn't!
I also feel that D&D (and its near derivatives) is uniquely suited to playing out coming-of-age stories. Even when PC's aren't literal teenagers, they often feel like they are. I've never seen a PC begin a campaign with a spouse or kids; oftentimes they don't have a job yet, until they begin the first adventure. If your character is level 1, that implies they lack experience (they literally have 0 experience! The game measures that!). As you play, the character learns about the world they inhabit, meets and forms relationships with new people, earns a reputation, and begins to advance their skills and abilities (by leveling up.) That's what being a teen and growing up is all about!