That is excessive, even though it includes cache files that are automatically deleted to make room when needed. Some apps take advantage of caching information even when not necessary, while the OS will cache information to speed up the computer by not having to turn to the HD or Internet for data used frequently. The OS manages its cache data much better than many apps.
A location on your user folder where some System Data collects is in the Application Support folder. You can remove folders from here for Apps that you no longer use, but do not attempt to delete anything else. You can view this folder by going to Finder > Go > Go to Folder, and enter "~/Library/Application Support" (without quotes).
You can also startup in Safe Mode to remove some of the system caches, then start again normally.
Start up your Mac in safe mode - Apple Support
It may also help to post the free EtreCheck report to identify problematic apps that are running on startup. There are 3 categories of apps that should not be installed as they are known to cause problems and it is best to remove these to see if the problem goes away before posting the EtreCheck report. The apps that should not be installed are:
- Cleaners (CleanMyMac is a known problem)
- Optimizers
- AntiVirus
Using EtreCheck - Apple Community