How to show random divs on page load?

I need to show 3 random divs on each page load. PLease help.

<div class="job-block1">
<h1> job block 1's content </h1>
</div>

<div class="job-block2">
<h1> job block 2's content </h1>
</div>

<div class="job-block3">
<h1> job block 3's content </h1>
</div>

<div class="job-block4">
<h1> job block 4's content </h1>
</div>