large sudden profiler spike

Hi i have virtually no experience with this. my game runs fine for a good while running 60fps but no matter where i go or what i do it eventually has this massive spike in rendering and physics and the game becomes unplayable.

is this garbage collection as people have said? I see there is a garbage collection aspect to the graph but it appears to be rendering and physics instead. how can i fix this? Just basic pointers if you can.. please don't use game dev jargon or acronyms too much thanks.