Screen is off when powering on pc but when restart it starts working,

Here are some ideas. Check them out and let us know how it goes.

First thought sounds like a video driver issue. If that is the case uninstall the driver in Device Manager and reboot the laptop and let Windows reinstall the driver.

Another thought is that it is set to external monitor. This is easily checked by connecting a TV or external monitor during the first powering on. Then look on your keyboard for the Function key for internal/external screen setting.