One way to Sign in automatically, or at least start the Sign in procedure automatically, is to:
1) Set your browser to startup with the same windows and tabs as last session;
2) End each browser session with a tab open that contains a page that requires your being logged in, such as Your Stuff>Private Messages (whether you actually need it or not); you may close down non forum pages before ending the session to avoid them at startup;
3) Upon startup, open the window with the tab in 2) and see whether you get signed in, otherwise sign in;
4) When you are signed in, go to your other forum tabs/windows and Reload each.
Especially if you have other things you may do, such as starting up other applications or feeding the birds, you may save some time.