What kind of plugins? Are they instruments? A lot of plugins use a lot of RAM so it can take a while to load them. And when you close the song it clears the used memory, which can take a couple minutes too. I regularly use about 20-30GB of RAM and it takes about 3-5 minutes to load everything and 2-3 minutes to clear it when closing, but I'm not using a hundred plugins I'm using anywhere from 20 to 40 and I just updated my system.
Check your RAM usage, make sure you're not using the pagefile / virtual memory, they are better than out of memory errors, but pretending hard drive space is RAM is insanely slow. If it is using the pagefile, get more RAM. The loading could have to do with that or with your hard drive type, if you don't have an NVME I would recommend getting one, but an SSD is still miles ahead of a platter hard drive. Or you just might have to wait for all of the plugin data to load and clear.
