New wrinkle

Turn off energy saving Sleep Mode in your OS settings.   It's nothing but trouble.

Nancy

With apologies for my earlier factious reply, we need to know more before we can give you a meaningful answer.

Does this only happen when you are not using the computer? If yes, how long does this need before happening?

Does this happen when the computer goes into sleep mode?

Or is it more than sleep mode?  Hibernate for instance?  If the latter, then hibernate is the work of the devil, and something I _always_ disable.  It also takes a chunk of your boot drive.

Does Photoshop shut down completely when this happens?  When you restart Photoshop, does it open with restored document s open in tabs?

What operating system are you using?

As much information as you can think of. The more you tell us, the better the answers will be.

It seems this problem is not unique to your computer and has an OS source. Google: mac shuts down randomly for a variety of possible solutions.

You might want to take a look at your operating system power saving settings

Dave

Make a recording of yourself singing a song, and play it back when you 'go away from your computer' so that Photoshop thinks you are still there.