Why is my Audi A4's engine making a knocking sound?

I've noticed that my Audi A4's engine has been making a knocking sound lately, especially when I start the car in the morning. What could be causing this and how can I fix it?

It's possible that the knocking sound is coming from worn out engine bearings. I would recommend taking your car to a mechanic to get it checked out and if needed, get the bearings replaced.

Another common cause of engine knocking is using low quality fuel. Switching to a higher octane fuel may help reduce or eliminate the knocking sound.