The sentence that you proposed is not good English. Relative clauses that modify a noun immediately follow that noun. (There may be some weird special cases that differ, but immediately following is the general rule.)
Thus either of the following is correct.
The person, who never gets tired, is reading.
The person who never gets tired is reading.
In spoken English, the relative clause bracketed by commas in writing, would be separated by brief pauses.
The two sentences have slightly different meanings. In the first, where the relative clause is bracketed, the relative clause is descriptive and not essential to the intended message that the person is reading. In the second, the relative clause is restrictive and just as important to the intended message that the person is both reading and has a significant attribute.