100% disk usage is either something scanning the hard drive, like antivirus, which should in theory stop at some point, or something using lots of memory, in which case it's using disk to page or swap programs from memory to disk.
Updates to windows and other programs generally use more memory as they add new features and bugs to fix with more updates to continue the cycle
You can bring up activity monitor and sort by memory utilization, see which programs are using the most memory, and if you really need them.
Then go into the control panel -> add/remove programs, and get rid of all the stuff you don't use, then reboot.
Also, if you have an SSD or NVMe solid state disk (non-spinning), they generally slow down as they get full. Get rid of stuff you aren't using (go into the disk properties and do the disk cleanup to get rid of temporary files and saved system states and update backups).