2013 Subaru Forester - ticking sound

My Subaru Forester with over 100k on the engine makes a ticking sound from the engine after running over 100 miles or so. It is a 2013. What is going on?

My wild guess related to valve train.
When idling or after switching the engine off?
Oil level checked?

Ask your shop to make sure all the spark plugs are properly seated.