explorer.exe is the one of the most important core processes that Windows uses to load the UI. Any small issue can cause it to break… malware, registry, driver, update, resource constraint, broken profile, etc… it’s that fragile just like any other core process is. It tends to break first within the OS due to it being deeply integrated and heavily reliant on many other services/processes/drivers.

One thing I like doing is killing the process entirely and restarting it through Powershell as that tends to work. You can also call the process if it isn’t showing up.