You're so right that 32 is young, and I have a few thoughts about it...
1) SO many FI/RE bloggers retired in their early 30s that it seems "normal" if you spend enough time on their blogs, but it does bring some challenges, namely, feeling like maybe you haven't contributed enough to society OR you haven't created your "life's work." Brandon
@madfientist has a couple wonderful posts/podcasts about his first few years after retirement where he talks about the importance of having a project you care about when you retire. One of the interesting things about following these online gurus is that they all have that project or purpose fairly well-defined, by nature of you even knowing about them! Certainly they do their own soul searching, but because they are bloggers and that gives them a sense of purpose and a channel for helping others, it's harder to look for them for guidance on defining purpose and meaning in your own life.
2) When you retire at 32, you aren't really retiring. Are any of us really retiring actually? It's really an opportunity to pursue work that matters to you, as MMM advises frequently in his posts. However, there's more constraints on work you're willing to do. For example, most of us would never work for a boss ever again. Nor would we want performance reviews or to be held to specific hours. So traditional work is out. You're right that starting a business (or in my case, pivoting the business I already own to something I enjoy more) can be a great path forward. So can volunteer work if you can find a cause you really care about. But this can still feel intimidating. Nothing worthwhile is easy! (Something I'm thinking about is taking a 2-3 year "sabbatical" to explore topics that I am interested in, almost like a self-guided master's degree, and see what comes out of that learning process.)
3) Many people in their early 30s have young children or are starting families, this takes a lot of time and you can genuinely be so busy with just this that it may be a while before you have the time and energy to pursue the passions you dreamed about pre-FIRE.
So to sum it all up, I think the most challenging, surprising and invigorating aspect of post-FIRE life is defining your identity and purpose, and what you could do if you could do anything.
Side note - I literally stopped working actively on my business on January 1, my baby was born February 1, and coronavirus started March 1. Our post-FIRE plans involve(d) quite a lot of international travel. We're optimistic for the future but it's definitely a weird time to embrace the retirement that you worked so hard for! I can't wait to reflect again on this same question a year or two from now!