As you go through the steps to complete auto the check-in request (on the “Boarding Pass” widget of for upcoming flight) switch "Auto check-in for every flight" on/off before tapping the “Save” button.

If you already submitted the check-in, tap on Status > then go through all the screens, and on the page with the "Cancel" button turn off "Auto check-in for every flight".

and tap the "back button" at the top left-hand corner.