#image {
  position: relative;
  padding-left: 25%;
  padding-top: 50px;
  margin-bottom: 100px;
  width: 50%;
}
img {
  position: relative;
  animation: move 10s infinite alternate ease-in-out;
}

@keyframes move {
  from {
    left: -200px;
  }
  to {
    left: 200px;
  }
}