You must reverse the word order…
"What your name is?" is ungrammatical. You must say "What is your name?"
English declarative statements normally put the subject before the verb. For example, in Your name is Jamius, the subject is your name and the verb is is.
English questions normally need a verb before the subject (except as explained below). If the question has an interrogative pronoun (who, what, where, when, why, how), the interrogative pronoun goes at the start of the sentence and the subject follows the verb. For example, What is your name?
The reason you cannot say What your name is? is because when the word order is not reversed, the interrogative pronoun is heard as a relative pronoun. For example, in I know what your name is, the word what functions as a relative pronoun: it makes what your name is into the object of know. Every interrogative pronoun can also function as a relative pronoun. Whether the subject precedes or follows the verb indicates which role the interrogative/relative pronoun is playing.
…unless the interrogative pronoun stands for the subject
However, when the interrogative pronoun itself stands for the subject, it still goes at the beginning of the question, even though this results in the same word order as a declarative sentence. Here are some examples.
Who is ready now? / Terry is ready now.
Terry is the subject of the declarative sentence. Since Who stands for Terry, the word order is the same in both the question and the declarative sentence.
What color is your parachute? / Your parachute is blue.
In the declarative sentence, parachute is the subject and blue is the subject-complement. Since What color in the question corresponds to blue in the declarative sentence, the question uses reverse word order. So, this question works just like What is your name?
How many people are in town for the weekend? / A hundred people are in town for the weekend.
Since How many people stands for the subject of the declarative sentence, a hundred people, the question has the same word order as the declarative sentence.
How long are these people in town for? / These people are in town for the weekend.
How long in the question stands for (part of) the subject-complement in the declarative sentence, so the question has reverse word order: these people follows are.
If you want a simple, approximate rule to remember, it's "Put the interrogative part first, followed by the verb, followed by anything else."
There's more to know about questions
There are some other important things to know about English questions, like the need to add an auxiliary verb (usually do) when the verb is anything other than be, and the fact that you can use the word order of a declarative sentence to make a question express surprise or emphasis (for example, Your name is WHAT??). Happily, though, the above is always correct when the verb is be.