If Notezilla works okay after you wait for sometime, then it means Notezilla is processing several notes.
Please go to the Notes Browser and go to your memo boards like Home and other memo boards and check the total number of notes that exist (see bottom right corner of Notes Browser).
If a memo board, especially the Home memo board, is having more than 100-200 notes, then it is better to organize and move them to another memo board.
Also check if the Desktop has many too notes. You can check the "On desktop" filter to see how many notes exist on the desktop.