I don't even know (rainbow boxes/spots/blotches/glitches?)

I've tried exploring and I still can't even find the issue or the solution. Can someone please help? There's like rainbow glitches all over my sim's model when viewing in rendered mode or material preview. I'd just switch the shading mode, but the wireframe..I just don't need that right now, and solid mode makes the entire model grey, and my sim's too pretty for that. Every forum I went to showed possible fixes but all of those had the old blender and I barely know how the new blender even works, let alone the old versions. Idk how to enter an image but I have a google doc with a couple screenshots if needed.