JSFiddle - React, Tailwind, and code Playground

HTML

<div id="box"></div>

CSS

#box{width:500px;position:absolute;top:0px;bottom:0px;left:0px;background:#ccc;}

JavaScript

box=document.getElementById("box")
box.addEventListener("mouseover",einblenden,false)
box.addEventListener("mousemove",einblenden,false)
box.addEventListener("mouseout",verstecken,false)

var timer;

function einblenden()
{clearTimeout(timer);box.style.overflow="scroll";timer=setTimeout(function(){box.style.overflow="hidden"},3000);}

function verstecken()
{clearTimeout(timer);box.style.overflow="hidden";}