Why does my Audi A4's engine make a strange knocking noise when it starts?

I recently purchased a used Audi A4 and have noticed that when I start the engine, there is a strange knocking noise coming from the engine. I'm not sure if this is normal or if I should be concerned.

This could be due to a faulty engine mount. It is recommended to have the engine checked by a mechanic to determine the cause of the knocking noise and prevent any further damage.

It is not uncommon for some Audi A4 models to have an issue with the timing chain tensioner, which can cause a knocking noise in the engine. It is important to have this checked and repaired by a qualified mechanic.

If your Audi A4 has high mileage, the knocking noise could be due to worn out engine bearings. It is recommended to have an experienced mechanic inspect and potentially replace the bearings to avoid any major engine damage.