unwanted reboot, closed programs, lost stuff

[cursor]

I closed my notebook computer for an hour or so. When I reopened it, the system had clearly rebooted – open programs had been closed, MUCH data was lost, my Chrome tabs were ALL closed ... and I see NO option to "reopen closed window".
+ Why did avast reboot my system?
+ How do I restore my previous Chrome working window/tabs?
+ How do prevent this from ever happening again without my express permission?

[Asyn]

Why do you think it's related to Avast..?

[cursor]

I strongly suspected.

Avast is the only new software installation. I've been doing this stuff since my original IBM PC – 1981, I think. I am completely familiar with all other very reliable application software on my computer. Given that, I assumed that it must be connected to an auto-update feature of this newly installed system utility.

[Asyn]

Sorry, but suspecting/assuming isn't something we can work with.

[Milos]

Hello,
in Windows' Event viewer (open start menu and search for "Event viewer") you should be able to find the reason of the reboot. Sort events by time and try to find "Shutdown Type".

Milos