popup when I set iPad down

When reading email on my iPad Air, iPad OS 17.3.1, if I set it down I get a pop up message that says Undo “X” with two buttons below that line , one for Undo and one for Cancel. The Undo “X” maybe Undo Read, Undo Write or strangely I have had an Undo Undo. What is the purpose of these popups and can I stop them?