SOURCE

<div>TEXT</div>

div {
    width: 500px;
    height: 150px;
    font-size: 100px;
    font-weight: bold;
    line-height: 150px;
    text-align: center;
    border: 1px solid white;

    background-image: linear-gradient(110deg, #999 10%, white 15%, #999 20%);
    -webkit-background-clip: text;
    color: transparent;

    animation: slide 4s infinite linear;
}

@keyframes slide {
    0% {
        background-position: 0px;
    }

    30% {
        background-position: 500px;
    }

    100% {
        background-position: 500px;
    }
}