How to execute Jquery code only once??

Use jQuery .one(). When using .one() method, the event handler function is only run once for each element.

$('#SearchButton').one("click", function () {
    $("#loadingMessage").css('padding-top', '6%');
});

$('#SearchButton').click(function () {
    $(".spinner").css('visibility', 'hidden');

    loaderStart();
    document.getElementById('loadinggif3').style.display = "block";
    $("#loadinggif3").show();
    $(".col-sm-9").css('visibility', 'hidden');
    var str = $('#SearchText').val();
    str = str.trim();
    if (str == "") return false;
});

Use a boolean as a global variable, like

var flag = true;

Now, set the condition before the execution, Like

if(flag){  
   $("#loadingMessage").css('padding-top','6%');  
   flag=false;  
}