Huge lag spikes when navigating between scenes? Is this normal

I’m new to optimization and a student, so excuse me if the solution is obvious or I am missing something. But I have been getting massive performance plummets when loading and navigating levels. While this is fine on my machine because I have a beast of a computer I want this game to be playable on a lower end PCs. Does anyone have any ways I can preload the scene or minimize the performance cost from switching over?

Thanks