<svg class="circular" viewbox="25 25 50 50">
  <circle class="path" cx="50" cy="50" r="20" fill="none" />
</svg>

.circular {
  width: 100px;
  height: 100px;
  animation: rotate 2s linear infinite;
}
.path {
  stroke-dasharray: 1, 200;
  stroke-dashoffset: 0;
  stroke: #000;
  animation: dash 1.5s ease-in-out infinite;
}
@keyframes rotate {
  100% {
    transform: rotate(360deg);
  }
}
@keyframes dash {
  0% {
    stroke-dasharray: 1, 200;
    stroke-dashoffset: 0;
  }
  50% {
    stroke-dasharray: 89, 200;
    stroke-dashoffset: -[-35px];
  }
  100% {
    stroke-dasharray: 89, 200;
    stroke-dashoffset: -[-124px];
  }
}