Make sure that if you’re using SceneManager in Unity, to unload the starting scene, so that when you go back to it the button’s state is reset.

Also try to make the game assets load gradually after the game loads, because currently it takes to long to even get to the made with Unity splash screen! Or maybe add a custom splash screen after the unity one (which I also do for my games) with the same background color to make the game first load your splash screen scene, then asynchronously load your game menu, instead of just staying plain gray until your menu shows!