How to determine if loading a form or submitting a form in hook_form_alter?
When there is no user input the form is loading for the first time and it is not submitting. 

Additionally you can check the entity whether it is new, if you don't want this condition to be true when the form is loading for an existing node:

if (!$form_state-&gt;getUserInput() &amp;&amp; $form_state-&gt;getFormObject()-&gt;getEntity()-&gt;isNew()) {
  // first load of the form
}