Startup of app is very slow from DVD


I have to distribute my app on DVD, but the startup is very slow on mac and windows (approx 2 minutes, 80 seconds for electron to load and 40 seconds for the main window to load content).
I tried nullifying the app with an empty page, but it doesn’t speed up at all.
The app is packaged with electron-packager.

Is there any way to speed up the electron startup, or at least show a loading screen?