I leave TeamViewer up and running in case I need to login. This morning TeamViewer was open on my monitor and I did not log in over the weekend. Does TeamViewer do any updates or work in the background if you are not using it?
Teamviewer has a log file where anything is logged with quite a lot details. You should find that log in the TV program folder.
I have seen Teamviewer misbehaving a lot in the past, but mostly on older versions. Current version 11 is stable so far. So, if the main window is open, s.o. may have logged in. This depends on whether your computer is well protected:
- do you use a random password? If so, you should use at least 8 or 10 alphanumeric chars, not the default 4-digit number.
- do you use a default password? I think so, because you wrote that you login from remote occasionally. Use a secure PW, see advices on the internet if needed! And probably change the current one.
I'm not sure about automatical updates, but IIRC, although I hardly ever changed the update configuration, TV always only notified me about updates and never took action itself. So an automatic update is unlikely.