If you combine the 3d graph with the memory usage you can see that the usage spikes with the 3d usage during the start of the game. It is most likely some form of resource binding taking place, pre-emptive setting up of texture addresses and pointers for gpu shaders etc.
I wouldn’t really be bothered with this, it’s not like the memory stays at a high level. It might even be some form of shader caching building the dervided data cache at the start.
Check if it repeats once your startup shaders are done compiling.