Learn German: Möchten Sie etwas bestellen? - Would you like to order something?

Because this sentence uses the formal "you", which is Sie. With Sie, the verb takes the -en ending. If you were asking a friend, you would use the informal du and say: Möchtest du etwas bestellen?

Why is the action verb bestellen at the very end of the question?

When you use a modal verb like möchten, it teams up with a second verb that describes the action. In German yes/no questions, the modal verb goes first, the subject goes second, and that action verb gets pushed to the very end of the sentence in its basic dictionary form.

Does etwas translate to "something" or "anything"?

It means both! German does not make the same strict distinction between "something" and "anything" that English does. The word etwas works perfectly here whether you mean "Would you like to order something?" or "Would you like to order anything?".

Why is Sie capitalized in the middle of the sentence?

In German, the formal version of "you" is always capitalized as Sie to show respect, whether it is at the beginning of a sentence or in the middle. If it were lowercase, sie would mean "she" or "they", which would change the meaning to: Would they like to order something?