В итоге нашлось решение через css без javascript :)
.startbox{-webkit-animation-duration: 9s;
animation-duration: 9s;
-webkit-animation-fill-mode: both;
animation-fill-mode: both;
-webkit-animation-name: fadeIn;
animation-name: fadeIn;}
@-webkit-keyframes fadeIn {
0% {opacity: 0;}
100% {opacity: 1;}
}
@keyframes fadeIn {
0% {opacity: 0;}
100% {opacity: 1;}
}
