Machine reboots after patches are installed if patches and reboot action are scheduled at the same time regardless of the time it takes for patches to install.
When patches are set to install at the same time as when the reboot action is set to reboot, the patches will install and take x amount of time. Then, when finished, the reboot action will take effect. In cases when many patches are schedule to install, assuming that patches take an hour or two to install, the reboot action will take effect immediately after.
Schedule the reboot action to occur before scheduling patches to install. This will prevent the reboot action from taking effect after patches are installed in cases when the time it takes for patches to install is well after the the time the reboot action is scheduled.
Internal Reference: SDP-196