Starts to lag BAD after a few minutes

I carried over my dada from my older PC to my new one via USB.  Its was 1.17 and it worked fine for the last month.  I have an MSI GE76 Raider with 16 GIG or ram and the GFORCE RTX 3060 video card.  When I open my world in 1.18 I can play for a few minutes then all of a sudden my guy is moving at 1 frame per second.  Very weird with the power my PC puts out in high end games.  Curious if this is a none bug or is my data damaged and/or replaceable?  Thank you