by itself; on its own
Как ни странно, дверь открылась сама по себе.
Strangely enough, the door opened by itself.
The Moon doesn’t produce its own light.
Да и куча леса сама по себе проекта мне не даст.
And a huge pile of timber by itself won’t give me a project.
Однако сама по себе эта штука не сработает.
However, this thing won't work on its own.
— 9th Company (2005)