Lightning Component:

<!--demo.cmp-->
<aura:component implements="force:lightningQuickActionWithoutHeader">
    <aura:html tag="style">
        .cuf-content {
        padding: 0 0rem !important;
        }
        .slds-p-around--medium {
        padding: 0rem !important;
        }       
        .slds-modal__content{
        overflow-y:hidden !important;
        height:unset !important;
        max-height:unset !important;
        }
    </aura:html>
    
    <!--Handler-->
    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />
    <aura:handler event="aura:doneRendering" action="{!c.doneRendering}"/>
    
    <!--Component Start-->
    <div class="slds-m-around--xx-large">
        <div class="slds-text-heading_medium slds-align_absolute-center">
            Loading...
        </div>
    </div>
    <!--Component End-->
</aura:component>

Lightning JS Controller:

({
    doInit : function(component, event, helper) {
        //Write your code to execute, before close the quick action modal
    },
    
    doneRendering: function(cmp, event, helper) {
        $A.get("e.force:closeQuickAction").fire();
    }
})