css (box-shadow) transition on page load

Question

Is there a way to make a transition happen for a box-shadow on page load instead of with a hover or click effect?

The transition I want on page load, or as an event:

.item:hover{
margin:0 auto;
box-shadow: 1px 1px 20px  grey;
transition: 0.7s;
max-width: 940px;
color: dimgrey;
padding-top: 10px;
padding-bottom: 10px;
border-radius: 10px 10px 10px 10px;
}

Answer 1

1. you can name keyframes a name and provide the time you need, I have provided4sec in the example.
2. It says change the background color from red to yellow and increase the height by 200px and animate this for 4 seconds.

.item {
  height: 100px;
  width: 100px;
  background-color: blue;
  animation-name: animate;
  animation-duration: 4s;
  border-radius: 10px;
}

@keyframes animate {
  from {
    background-color: red;
  }
  to {
    background-color: yellow;
    height: 200px;
  }
}

<div class="item">

</div>