RainMaker by design will not log you out unless you click the logout button.
Are you using a tablet or a desktop?
If it is a tablet, the tablet literally shuts itself off breaking the connection to RainMaker. Without a connection to RainMaker it has to log you off. It is a function of the Tablet, nothing RainMaker can do to keep you logged in. You will just have to log back in.
If it is a desktop, then you need to adjust your settings to not allow your computer to go to "sleep."
You can have your monitor go to sleep, just not the computer.
If your computer goes to sleep, it cuts it's ties with RainMaker, logging you off.