How to diagnose engine issues in an Audi A4?

I've been experiencing some trouble with my Audi A4's engine lately. How can I diagnose and troubleshoot any issues that may be present?

First, start by checking for any warning lights on the dashboard. If there are any, take note of them and do some research or consult a mechanic for further guidance.

You can also use an OBD-II scanner to check for any error codes. This can give you a better idea of what could be causing the issue.