It depends on the OS where the log files are.

  • C:\Documents And Settings\All Users\Application Data\Avast Software\Avast\Log
  • C:\ProgramData\Avast Software\Avast\Log. Some may also be in the respective \Report folder.
  • C:\Users\All Users\AVAST Software\Avast\log

What will be in them depend on the settings you have made for logging.

I suggest you also check the Windows log files to see if they show anything that could be related to the problem.

As for the shutting down, I suggest you give the laptop a good cleanup.
Removing all dust (outside as well as inside) as well as removing all not needed (temp and otherwise) files.
Also never put a laptop on a flat surface.
Air need to be able to flow underneath a laptop as well as over it.