18.10 – Micro-lag with a new installation of Ubuntu Cosmic

I have recently upgraded (new installation) of Ubuntu 18.10 on my PC with the help of an Asus P8Z77-M motherboard (using Intel HD graphics), 24 GB of RAM and an Intel SSD.
However, I have noticed a lot of microlagging since the installation. For example, I am going to type and the letters being typed are sometimes delayed by one second. The music being played also pauses for one second before resuming.

The graph of the CPU is flat (10-20% on average).

Release lshw -c video

*-display
description: VGA compatible controller
Product: Xeon E3-1200 Graphics Controller v2 / 3rd Gen Core Core
Seller: Intel Corporation
physical identifier: 2
bus info: pci @ 0000: 00: 02.0
version: 09
width: 64 bits
clock: 33 MHz
capacity: msi pm vga_controller bus_master cap_list rom
configuration: driver = latency i915 = 0
resources: irq: 29 memory: f7800000-f7bfffff memory: e0000000-efffffff port: f000 (size = 64) memory: c0000-dffff

Everything else works well quickly. The videos play well. The mouse is not slow. Ideas?