Hi Jo, my name is Neil, I'm an independent adviser and a Windows 10 user like you.
Sorry you're experiencing problems with your mouse cursor.
This is activated by clicking down on the mouse scroll wheel.
Yes, the mouse scroll wheel as well as scrolling up and down is also a clickable button like your left and right mouse buttons. So pushing down on the wheel will activate the cursor pointer you're describing. Then moving your mouse up or down will make the page scroll up and down faster or slower depending on how far you move your mouse.
Clicking the Mouse wheel a second time will return your mouse to it's normal state.
Some computer mice have a very sensitive scroll wheel where you can accidentally click it down very easily whilst scrolling, so you have to use a lighter touch as not to activate clicking the wheel down.
I hope this answers your question.