32 years ago I went to a salvage yard and picked up 3 hollow core doors. [Light weight, 36”wide all the same size]
I screwed 2x4’s on for the legs, then cut plywood triangles to stabilize the frame on each shelves.
I made several, on one I got a solid core, cut it in half and used it for the end and legs.
Then I put rollers on the 4 legs. I still use it.