Sadly, Emacs (unlike Spacemacs, which has spacemacs/find-dotfile) doesn’t have a function to open its own init file, so thousands of users have to write their owns. I’m not different :)
Using use-package:
(use-package iqa
  ;; use this if your config is generated from org file
  ;; :custom
  ;; (iqa-user-init-file (concat user-emacs-directory "README.org") "Edit README.org by default.")
  ;; bind iqa functions to shortcuts
  :bind (:map ctl-x-map
              ("M-f" . iqa-find-user-init-file)
              ("M-c" . iqa-find-user-custom-file)
              ("M-r" . iqa-reload-user-init-file)
              ("M-d" . iqa-find-user-init-directory))
  ;; :config
  ;; (iqa-add-bookmarks) — to add bookmarks to emacs init files
  ;; (iqa-setup-default) - to bind default bindings
  )or just put iqa.el to load-path and
(require 'iqa)
(iqa-setup-default)iqa-find-user-init-file is a shorthand to open user init file.
  By default user-init-file is used.  If your configuration is generated
  from org-mode source you may want to point it to your org file.
(setq iqa-user-init-file (concat user-emacs-directory "init.org"))File is opened by find-file but you can redefine it by e.g.
(setq iqa-find-file-function #'find-file-other-window)iqa-reload-user-init-file reloads user-init-file (not iqa-user-init-file)
For a full restart take a look at restart-emacs package.
iqa-find-user-init-directory opens init file directory
iqa-setup-default defines keybindings:
C-x M-f — iqa-find-user-init-file
C-x M-c — iqa-find-user-custom-file
C-x M-r — iqa-reload-user-init-file
C-x M-d — iqa-find-user-init-directory
If you don’t like these, or prefer to use Emacs bookmarks instead, iqa-add-bookmarks
  adds bookmarks to these files.