I apologize if there is some obvious answer I'm not aware of but I've found that the quickest route to resolving almost any software issue is to ask a question on a forum which at the very least will spawn ideas or hints pointing the way to resolution.
That being said I've been using Photoshop since version 4.0 i.e Windows 98. In all those years the Clone tool has always been a straight forward affair... Select the tool hold down the alt key > click to select the "Begin sample area" then start painting. Really nothing to it. this morning I select the tool and when I move my cursor onto the canvas the canvas jumps to some new position "AWAY" from the area that I want to work with. And refuses to be or stay where I want to work.
OK I figured this on out. The brush tool was set from the last time / project I used it on to a size that was about 90% of the image size of this new project. So I click select the Clone tool and move my cursor onto my canvas and my brush sixe is huge (relatively ) and the 500 X 400 canvas immediately centers to the center of my 450px brush. That frankly, was maddening. Solution was simple, change brush size to something more reasonable. In this case something like 9px. Curiously though I see the tool opens with a sample already apparently selected, which is something I don’t remember it doing before. That in part was what was causing me the confusion. The entire image was under the brush which was so big its bounds (the circle that is the brush size) exceeded the view of the screen. And because I was entering the screen from the tool bar the center of my brush was first and immediately on the left edge of the screen. So my screen /view immediately jumped to the left where the center of my brush was.