Yeah, the FOG log on the client (C:/fog.log by default) would probably tell you why the client was rebooting the computer. You can also check if forcerestart=1 in C:\Program Files\FOG\etc\config.ini.
Reboot options can be set several ways in the FOG manager too:
[B]Auto logoff[/B]
[LIST]
[][B]FOG Configuration > Auto Log Out[/B] or
[][B]Other Information > FOG Settings > FOG Service - Auto Log Off[/B] or
[*][B]Group Management > [I]myGroup[/I] > Service Settings[/B]
[/LIST]
Remember that “Auto logoff” reboots the client computers after it times out.
[B]Task reboot[/B]
[LIST]
[][B]FOG Configuration > Task Reboot[/B] or
[][B]Other Information > FOG Settings > FOG_SERVICE_TASKREBOOT_ENABLED > 1[/B] or
[][B]Group Management > [I]myGroup[/I] > Service Settings[/B]
[/LIST]
[B]Shutdown/Reboot[/B]
[LIST]
[][B]FOG Configuration > Green FOG[/B] (Only if no user is logged in) or
[*][B]Group Management > [I]myGroup[/I] > Service Settings[/B]
[/LIST]