Why does my Audi A5's engine make a loud knocking noise when starting?

I have noticed that my Audi A5 makes a loud knocking noise when I start it, especially when the engine is cold. Is this a cause for concern? What could be the potential sources of this noise?

The most common cause of a loud knocking noise when starting your Audi A5 is a worn out spark plug. This can lead to rough engine running and decreased fuel efficiency. It is important to get your spark plugs checked and replaced if needed.

Another possible source of the knocking noise could be a faulty fuel injector. This can cause your engine to misfire and may also result in a decrease in performance. It is recommended to have your fuel injectors inspected and replaced if necessary.