Sometimes, when we say "Nobody wants me to do what I don't want to do？", I was always wondering and dying to know if I could say "Nobody wants me to do what I don't want to" instead? Thanks.
British English is much more likely to include the do. Most Americans omit it whenever we can get away with doing so, and would probably prefer the "Nobody wants me to do what I don't want to" form.
In English, there can be ellipsis of a verb clause.
Nobody wants me to do|| what I don't want to do||.
In this case, you cannot leave out the do. Because there is a complex sentence made up of a main clause and a subordinate clause.
You can only leave out repetition of the verb that comes after to when the context is clear. That said, some people in speaking might very well leave it out: Nobody wants me to do what I don't want [to do].
Person One: I want you to go to the movies with me. Do you want to? [you can leave out repeating go] Person Two: Yes, I want to. [to go to the movies, implied]
Person One: I want you to do this, I insist on it. Person Two: Why do you want me too? [to do this].