Vendoz That's suspicious actually, install security suite on server cpfence or cpguard and see if any malicious activities being caught. Secondly, if all or majority of your sites using WordPress then install litespeed caching + enable redis + make sure opcode caching in enhance is enabled in every sites optimization settings.
Do some trial n error, this is a lengthy process but trust me you'll find best tunable settings in this, Start by setting 1vCPU, 1GB RAM, 20NPROC, in next configurationlimit on IO and IOPS, Set IO between 10MB/s to 30MB/s, IOPS to 1024 - 2048
Next tune your database using my.cnf, use platform like reeleem (releem.com), they offer decent free tier for one database instance and give 10 optimizations, but you have to setup it according to enhance, follow this guide thanks to @ivansalloum (https://ivansalloum.com/how-to-install-releem-on-enhance-control-panel/), which is decent starting point.
Another method is search database optimization in this forum and play arround till you find best performance.
