An online test for your enneagram can be found here:
http://www.eclecticenergies.com/enneagram/
It's sort of a new age mysticism site, but it provides two different styles of test that you can cross-reference. There's plenty of other tests online you can take if you Google it. You can also read descriptions that provide different viewpoints on what all the types actually mean.
They probably are not very accurate since they are just online tests, so it's good to keep in mind that it is just for fun.
And you can see which characters have the same type as you by referencing the Xenoverse Study Guide:
http://xenoverse.xenotensei.com/characters
I pretty solidly fell into the Type 5 category.
World View: The world is invasive and confusing. I need privacy to think.
Basic Desire: to understand the world
Basic Fear: of being overwhelmed by the world
So, I scored closest to Wilhelm. I thought that was kind of amusing since it says a few things about my personality. Detached, a tendency to retreat into my own thoughts. Keen focus on particular subjects with a desire to be adequate and meaningful. The other characters with this type are Kevin and Joachim Mizrahi. I share a few of their traits, too.
It's hard to know a lot about Wilhelm from just the game, since he is so mysterious. But I think that I do "get" a lot of the notes on him and his Enneagram type in the ODM and other resources.
Particularly, a sense of meaninglessness. A fear of being inadequate or lacking the inner strength to deal with the world that everybody else seems to exist in with no problem. I have no established religion or spirituality, and it is very difficult for me to form personal relationships.
If this was part of Wilhelm's internal struggle and his motivation for putting eternal recurrence into action, then that would be pretty interesting to me.