comma with 'itself' [pronoun]: the train, itself, began to move

[Eerie]

Which is correct? With or without the comma?
A. The train itself began to move.
B. The train, itself, began to move.

Does the word "itself", in that sentence, function as an adjective?

 

[Pidginboy]

The train itself began to move.

But a more idiomatic way is : The train moved on its own.

 

[panjandrum]

Which is correct? With or without the comma?
A. The train itself began to move.
B. The train, itself, began to move.

Does the word "itself", in that sentence, function as an adjective?

What does the sentence mean?

Do you mean that the train began to move of its own volition?
If so, then itself is a pronoun and is part of the adverbial phrase by itself in which by has been elided.
It would be better to place itself at the end of the sentence.
The train began to move (by) itself.

Do you intend itself to be emphatic?
It is still a pronoun
I don't think you should use commas to isolate itself.

 

[Eerie]

Sorry, I couldn't think of a good example. But that answers my question, thanks!