That's not a workaround - *somebody* still needs to log on to PC, so the original question still remains......
My interpretation was different. If one goes to:
System / Administration / Login Screen
and selects 'Unlock' and then 'Log in as <user> automatically'
then when rebooted, the login is bypassed and TeamViewer starts without user intervention. I suggested it was a work around although it may be totally unacceptable from a security standpoint. As an aside, I found an article that explains how to use VNC to gain access prior to login. The only thing I don't like about this technique is that it starts a different session ie, Display 1 compared to the session you would have if you logged in. This may or may not present a problem to me.