How can I troubleshoot the ignition issue in my Audi 80?

I recently bought an old Audi 80 and it has been having issues starting up. Sometimes it starts fine, but other times it won't start at all. How can I effectively troubleshoot and fix this ignition issue?

First, make sure the battery is fully charged. If the battery is new, then the issue may lie with the starter motor. You can use a multimeter or have a mechanic check it for you.

Another potential cause could be a faulty ignition switch. You can use a code scanner to check for any error codes related to the ignition switch, or again, have a mechanic diagnose the issue for you.

Check the spark plugs and wires, as they may be worn out and need replacing. A quick visual inspection can tell you if they need to be replaced.