SYMPTOM
Even after setting the startup type on the Strategy Service Manager to manual, Strategy Intelligence Server starts up after system reboot. As seen in the screenshots below, the startup type is seen as manual on the Strategy Service Manager and also on Windows Services.

CAUSE
This is working as designed. When re-starter is enabled (under Options > Intelligence Server Options) on the machine and even if the startup type is manual, if the Strategy Intelligence Server is running before system reboot, the Strategy Intelligence Server starts up upon system reboot. If the Strategy Intelligence Server was not running before system reboot, it will not start when the startup type is set to manual.
ACTION
There is no action that needs to be taken as this is working as designed.