Loading interstitial adMob in different threads
There is no need to use Thread class you can directly do this:

// loading ads
    handler = new Handler();

            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    loadInterstitialAd();
                }
            }, 5000);


So what is happening your handler will schedule your Runnable after 5 sec, you don't have to instanciate Thread and call runnable again.