Long sleep on iMac results in restart

[YMark]

Ever since I upgraded to Sierra, when my iMac goes to "sleep" for the night, it ends up restarting. For example, when I go to use my iMac the next day, I'm looking at the Login Screen. It has obviously restarted. All programs open as they would if I manually restarted and chose that option.

Has anyone else experienced this? I also have an Air running Sierra and it doesn't do this.

Thanks

 

[marvz]

Do you also get an error message about a sleep/wake failure? It happens with my iMac since 10.12.1. I had this problem a few months ago but it disappeared on its own and now came back with the update.
I read a little and found it can be related to upgraded RAM, attached USB devices and maybe Dropbox. Also someone mentioned to deactivate the screensaver.
All in all it also has to be software related since it clearly came back with 10.12.1 for me.

 

[YMark]

I found my issue. It wasn't a reboot, it was an automatic logout. Not sure exactly how this got flipped, but it started when i installed the last beta of Sierra. Anyway, the fix was in the Advanced tab of Security and Privacy.

 

[marvz]

Ah okay. So it's something different. At the moment deactivating the screensaver has kept my iMac from getting the sleep/wake failure.