My three wired optical mice do that. I think it's an optical quirk.
I just bought a USB wireless mouse today for my notebook. I see that sometimes while mouse is idle, my cursor automatically shakes and moves a little( just like trembling and moving a bit from its original place and going away gradually). It,s a bit annoying for me. Is it usual with wireless mouse or my mouse is not good one, or may be something in settings etc?

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