It can be due to
PSO Compiling (try force precaching)
or the issues with the sync policy.
Try using -DPCVars=“nDisplay.sync.nvidia.UsePresentBarrierPolicy=1” in the command line
This cvar allows to replace the original NVIDIA sync policy with the new Present Barrier (DX12 only).
While in testing, it’s controled by this cvar. Later on, Present Barrier policy will be exposed to
the GUI configurator as well as other policies are.