CPU usage really depends on a lot of factors. The biggest ones are:
- Amount of asset scanned at the same time.
- Amount of scanning threads configured (Configurable in Configuration\Server Options)
- Amount of extra scanning items configured (custom file scanning and registry scanning)
- Amount of data scanned for Widows items ( https://www.lansweeper.com/kb/115/managing-how-often-specific-data-is-scanned.html )
- Amount of queries being run
- Amount of emails being processed
As a starting point, I would go through this knowledgebase article to clean up your database which can help: https://www.lansweeper.com/kb/147/clearing-tables-to-free-up-space-and-improve-performance.html
If it doesn't help, I would start looking at the other items I've listed and checking which one might be causing the issue.