Are you disabling the Connected Standby on registry? If you disabled the Connected Standby, it will not sleep anymore, it will directly hibernate when you press the power button or close the dock.
If not, check the power setting on control panel, you probably set it to directly hibernate or shutdown on closing lid.
Also this tablet will automatically hibernate after 1 hour sleeping, you can disable it in the same setting.
It would be the best what setting have you done on the tablet, as normally this tablet will behave like a tablet/laptop.