I have the same problem on my laptop.
When I let it without touching anything, the laptop goes to sleep mode. Until there, everything is normal.
But when I try to come back on the computer from sleep mode, the computer restarts. I mean, there are same screens, every windows are closed and I have to open everything again. The same thing happen is I go to sleep mode by using the button.
I bought my laptop a month ago and everything was going well at the beginning. I guess it started after an update of something. I tried to install the latest driver for the graphic card in case, but it's still the same.
* I also tried the CPU diagnostic
If anybody has an idea.
Ps: Sorry if my English is not good enough but it's not my mother tongue...