blue screen when connecting to my mac mini

I use team viewer to access my mac mini when I am away from home.  Generally it works well but about once a week, when i try to connect, it will connect to my mac, but just shows a blank blue screen with no option to login.

usually when I connce it will show me the osx login.

when this happens the only solution I have found is to reboot the mac.  unfortunately if I am not home then I am unable to do that until I get home.

any ideas why this might be happening?