Just saw the same weird thing happen on two different computers. Windows had opened each One Drive I have installed.
I have three (3) MS One Drive accounts. And all three are enabled on two different computers. One is my home computer and another is a workstation I remote into. I had both open via Remote Desktop, and all the sudden all three One Drive folders were opened. I didn’t actually see them open up. Just when I switch back to the RD connection, the windows task bar showed each one being open.