First, upgrade the BIOS and Power Management driver for your specific machine.
Now go to Windows Power Management settings. I suggest you use Suspend and not use Hibernate or Hybrid sleep. Hibernation has had more than its fair share of issues.
Having set to Suspend, set the Suspend time (completely idle time) of 30 minutes or 1 hour.
Restart to make sure the settings take effect.
Now check that the machine does not suspend on its own if you are using it. You may have a battery issue.
Set as above works very well for me. I know my battery is good.
If these things do not work, try creating a new operating system on a new disk.
This will help divide the problem in two between operating system (new install does not fail) or hardware (new install fails the same way).