https://developer.mozilla.org/en-US/docs/Web/API/setTimeout

Wrap the entire script inside a named function block and call that from a setTimeout function:

(run the snippet and wait 4 seconds to see console message)

setTimeout(scriptCode, 4000);

function scriptCode (){
// place all script code here;
console.log("done");
} // end script

If you must reference the script from a named url, you can assemble a script tag in js and append it to the page after four seconds. Like this:

    setTimeout(scriptCode, 4000);

    function scriptCode (){

    const scriptElement=document.document.createElement('script');
    scriptElement.setAttribute("src", "http://scriptAddress.com");
    scriptElement.setAttribute("async", "");
    document.body.appendChild(scriptElement);

    } // end script

The script tag will be added to the DOM after 4 seconds and will load and execute as normal