I'm new to using Google Forms and have added all my questions. Is it possible to automatically add question numbers or do I need to go back and manually write them at the beginning of each question?
Your best bet is to simply add a question number to the begining of each question.
1) What year were you born?
Then you can go to your response spread sheet and put a more "code" oriented column header, or even move the columns to match the order of the question.
For example in your responses spreadsheet:
Row 1, machine readable answers, or anything you'd like: "foo, bar"
Row 2, your actual questions from the form: "I am Question Foo?, I am Question bar?"
Row n, responses: "..."
The Google Forms UI doesn't has an automatic question numbering feature, like pressing a numbered list format button, but this feature could be added by using Google Apps Script. Maybe someone already did for you, so take a look to the add-ons store before you write your own script. For further details see Use add-ons and Google Apps Script