Microsoft decided to move the Start Menu into its own process. Starting with Windows 10 v1903,(Windows 10 19H1 ) there is a separate process available for Start Menu / StartMenuExperienceHost.exe.
Current Start Menu iterations rely on Explorer Shell; if anything slows down the Explorer process, the Start Menu is slowed down as a consequence as well. Microsoft separated the Start menu into its own process, called StartMenuExperienceHost.exe. This has a number of benefits, including simplifying debugging and insulating Start from potential issues impacting other surfaces.
The Start Menu process is StartMenuExperienceHost.exe; it is introduced with the May 2019 Update and users will see the process listed when they open the Windows Task Manager or use another process manager or explorer on the machine.
By cutting the tie between Start and Explorer, issues that affect Explorer won’t impact Start anymore once the May 2019 Update for Windows 10 is installed on a device (or newer versions).
Restart Start Menu (StartMenuExperienceHost.exe) in Task Manager Processes tab
1- Open Task Manager (Ctrl+Shift+Esc) in more details view.
2- Sort the processes by name, and scroll to find a program with name Start. And, Right click on Start, and click on End task.
3- The start menu process will shut down and restart after a second or two.
Add Restart Start Menu Context Menu in Windows 10
1- Download the .zip file to your computer. And extract the files.
2- Right click on the Add Restart Start Menu To Context Menu.reg file and select Merge. Confirm the User Account Control dialog if prompted.
3- Click Yes to continue.
4- Registration entries are successfully added to Registry. Click OK.
5- Again, later on, if you want to remove the menu, then run the Remove Restart Start Menu From Context Menu.reg