I'll have the same problem with a small 200mb scene. If I use more than, say 200 samples, then the scene will crash. If it actually was a memory problem, then Blender would give you the error: Out of memory. A few things I have uncovered that help me with this is using less samples, denoising, and using smaller size tiles for rendering. (CPU). Using larger tiles for your GPU may also work. Blender will also crash if your CPU is slower than the minimum speed for processing a huge render. One last thing that might help is to use more CPU threads. More threads will use more of the CPU, so that more of the CPU is used for rendering. This may help Blender to not crash. I compared rendering a scene on one thread as opposed to 250, and there was a big difference. The downside to using more threads is that the rest of your computer may run slower. These are just some options for rendering, but I hope at least a few help.