Cycles rendering unwanted animation

Out of the blue, Cycles - not Eevee, closes down the rendered image and immediately starts rendering again, as if it wants to do an image series for animation. The model has never been animated and I don’t do animations. I’ve checked the timeline - nothing there, but to be certain, I’ve set everything I can find to start 0, end 0, steps 0.

I’ve probably inadvertently set something to do a series of renders, but can’t for the life of me find where.

Blend file

Keep safe:)

You have two View Layers, both set to render

Thanks so much, John - really saved my bacon there:)