jeerose is correct, but I will attempt to help you anyway.
The problem is how the plugin works, mostly these lines:
if(options.auto && dir=="next" && !clicked){
timeout = setTimeout(function(){
animate("next",false);
},diff*options.speed+options.pause);
};
What this is doing, is if you cliked on a buttons like next, back, or in your case 1,2,3,4,etc... then it sets clicked as true, and won't run the animate function automatically any longer. There are a number of ways to fix this including writing your own wrapper plugin that defines the easySlider and has implements it's own click handlers, sending false for clicked instead of true like they do currently. The other option is to just edit the source file itself. Change the code I have listed above to:
if(options.auto){
timeout = setTimeout(function(){
animate("next",false);
},diff*options.speed+options.pause);
};
This will make it so the auto play never gets disabled provided you have set "auto" to true when creating your easySlider.