Yeah my number 1 question when creating a character is “why are they an adventurer?” This also means that you will have a motivation that you can use to ground your decisions. I’d recommend if you haven’t already seen it to check out this video. It’s long but is a fantastic explanation of what is important to think about in order to roleplay. It has nothing to do with a funny quirk or voice, and has everything to do with understanding your character’s motivation.
You still haven’t shared anything about your character with me, but if you want some ideas or brainstorming I can definitely help out. I’d need to know their race/class/background/subclass and any backstory details you’ve already established.