I have faced the same issue yesterday with my server...
My server details:
CPU Model: Intel Xeon Processor (Skylake, IBRS)
CPU Details: 1 Core (2100 MHz)
Distro Name: CentOS Linux release 7.9.2009 (Core)
Kernel Version: 3.10.0-1160.49.1.el7.x86_64
Memory: 2GB
The only solution that made my server go back again and work normally with ClamAV and AmAvis up and running was to create a swap image. I add a 4GB swap image and after a server reboot, both ClamAV and AmAvis started normally and did not take CPU time abnormally.
Here is a tutorial on how to create a swap image on Centos 7 CWP ->
https://www.mysterydata.com/create-and-add-swap-on-linux-os-cwp-centos-webpanel-and-vesta-cp/The main problem that I have faced is that AmAvis could not find a socket and connect to ClamAV. This is an error I found in maillog: "host amavis[1975]: (01975-01) (!)connect to /run/clamd.amavisd/clamd.sock failed, attempt #1: Can't connect to a UNIX socket /run/clamd.amavisd/clamd.sock: No such file or directory"
The clamd.sock file was not created after restarting ClamAV service or server reboot. After swap image creating and activating, that file was created automatically when I start the ClamAV service.
Hope that this would help someone with the same issue.