Pretty much all the time. The chair I'm sitting in wasn't caused be me, and vice versa.
No, but there is a correlation between the chairs position, and your position while sitting in that chair.
And arguably it is partially causative. The reason you are sitting there is because the chair is there. If the chair were 2 ft to the left, you'd be sitting there instead.
Chairs can be moved though; sometimes I'm sitting there because that's where the chair is, but sometimes (like in my apartment) the chair is where it is because I put it there because I like to sit sometimes and that's a good spot
And yet, I didn't cause the chair, and the chair didn't cause me.
There is more to causation than 'creating into existence'.
Quite. This is just one of the many examples of "correlation is not causation".