Change your password. Easy as that.
You are in charge of who is using your account. If someone else has access to it, you apparently keep yourself automatically logged in on a device someone else has access to or you have share (knowing or unknowingly) your password with someone.
Changing your password usually fixes that. That includes the password to devices you keep yourself automatically logged in.
We can not see who is behind the screen, so we don't know when it is "you" or someone else.
Locked.
