Please check the device settings:
1) Go to the recording Menu (press menu button) -> Loop recording -> select length of recorded file. When there will be no free place on SD card, the device will automatically overwrite files, starting from the older ones. Device will be recording continuously.
If this option is off, device is recording only one file. When SD becomes full, the device stops recording and turns off.
2) LCD / device is turning off automatically - it can be set in Setup menu (press menu button 2 times) -> LCD Auto off / Auto on