Virtualbox freezes, CPU usage fluctuates. What is the reason?

Question

linux

Host machine - FX6300, 16gb ram, ssd, OS Linux 5.9.10-1-MANJARO.
In a windows server 2003 sp2 virtual machine. 1 core, 256mb ram, 4gb per ssd.
The system works with freezes (freezes for 100-200ms with a period of 1-2s), htop shows short-term load jumps up to ~ 30%. Tried all types of virtualization, chipset, turned off AMD-V, does not help. Just in case, the virtual machine is attached to one processor core. In the device manager, 99% - system inactivity, no load.

Answer 1

This is

256mb ram