Quote Originally Posted by Alex80 View Post
At the same time "находить" in the first meaning "to walk on/over/atop something" with self-action (return-action) particle "-ся" that is "находиться" is "to walk on/over some location (not leaving it)", so it become "to be located on/in".
I believe, it was the second meaning (“to find”) that the word находиться “to be located” was formed from. The suffix -ся marks passive here. «Что-то находится где-то» — (literally) “Something can be found somewhere” — “Something is located somewhere”.

Moreover, находиться is most likely a calque of German sich befinden “to be located” (lit. “to find oneself”).