Mac Completely Crashes and Turns Off

Hi everyone, I’ve been having this issue the past couple of days now. When I play the game, certain actions cause my computer to completely freeze and ultimately shut down in its own, telling me it shut down due to a problem upon reboot. This has never happened before. I do use quite some mods, but I’ve recently gone through and cleaned out some old ones and updated some corrupted ones. I have also deleted some other things to free up general storage on my iMac. I have a 2019 iMac with 3.6 GHz Quad-Core Intel Core i3, Radeon Pro 555X 2 GB graphics card, and 8 GB 2400 MHz DDR4 memory. 
Today, the computer crashed when I was in that free camera mode giving myself a tour of my new house. Later on, the computer crashed when I tried to save this lot to my gallery. 
I’m feeling defeated. I can’t afford a bigger, better computer right now and my free time is limited. It really sucks having this take up so much time.