That sounds like the main character Roger from the animated show Big O. I'd look take a look at him. He's a character that wanted to forget and is fine without his memories. It's strongly implied that he was a very different person before he lost his memories. Watch the episode "Big O - Roger the Wanderer". Roger in the Black-suit is the main post-memory loss self and the ragged tan coat Roger is the pre-memory loss self. See it on YouTube here: Part 1, Part 2, Part 3. Funny enough, re-watching the episode again it heavily implies that all of the characters are changed because of their own memory loss.
In almost every example of this I can come up with, amnesiac characters almost always becomes opposed to whatever they were doing before they lost their memory. I think it's a nice symbol for how we all have deep regrets, and chore-y things we do because we have to (e.g. being stuck in a job we hate because it's a reliable source of being able to eat). Losing all your memories means you get to start from a blank slate, free of all that.
as someone mentioned earlier, while basic personality traits might still be present, it really is the chain of everything that's happening in your life that shapes who you become and how you behave. You shape the way you talk after your idols, you make your decisions based on your upbringing, your fundamental personality traits come primarily from your environment.
If that's ALL gone then you're a blank slate again, likely need to re-learn how to speak as well., thought basic motor functions may remain just fine
