Check your drains.
I have to clean the drain pipe in my shower because the walls of the pipe gets a ring of hair, grass, or whatever will stick to the pipe at the trap.
A quick swipe with a pipe cleaner looking brush that Sandy found, and a spritz of bathroom cleaner, makes our problem go away.
Though this works for me, your mileage may vary.
Welcome to the forum!
P.S. Howdy PQGlen!