While it feels odd initially that どこか, can be used in a “somehow/in some way” sense, I can learn to recognize that. But I’ve also learned that なんか is also used to mean “somehow”, so can anyone help me distinguish
今日の父親の様子はどこか変だと思う。
and
今日の父親の様子はなんか変だと思う。
?
I think it’s just a difference of formality. なんか feels slightly more causal. どこか feels slightly more formal.
While どこか and なんか are used similarly in this situation, they do carry a slightly different nuance. When we use なんか it has the nuance of a more general feeling. You’re not sure if it’s something specific, or the whole thing. When we use どこか however, it tends to point towards a specific behavior or more detailed part and not the subject/person as a whole. A good way to remember this is that なに or なん is almost always used as an open question with a large variety of responses. While どこ is asking for very specific information.