Сайт дергается вниз после загрузки и при проигрывании первой анимации

html {
  box-sizing: border-box;
}

*,
*::before,
*::after {
  box-sizing: inherit;
}

body {
  font-family: 'Inter';
  font-style: normal;
  font-size: 16px;
  font-weight: normal;
  color: #FAFAF9;
  position: relative;
}

.custom-btn {
  padding: 24px 74px;
  color: #fff;
  border-radius: 10px;
  padding: 10px 25px;
  background: transparent;
  cursor: pointer;
  transition: all 0.3s ease;
  position: relative;
  display: inline-block;
  box-shadow: inset 2px 2px 2px 0px rgba(255, 255, 255, .5), 7px 7px 20px 0px rgba(0, 0, 0, .1), 4px 4px 5px 0px rgba(0, 0, 0, .1);
  outline: none;
}


/*Header styles start*/

.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 2;
  background: #0C0B0B;
}

.header_wrapper {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  padding-top: 54px;
  padding-left: 6px;
}

.wrapper {
  max-width: 1520px;
  margin: 0 auto;
}

.header_list {
  margin-left: 330px;
  left: 0;
  display: flex;
  flex-wrap: wrap;
  padding-bottom: 16px;
}

.header_item {
  margin-right: 46px;
}

.header_item:last-child {
  margin-right: 0px;
}

.header_link {
  font-size: 26px;
  line-height: 31px;
  color: #FAFAF9;
  text-decoration: none;
}

.header_link:hover,
.header_link:focus,
.header_link:active {
  opacity: .75;
  text-decoration: underline;
}


/*Header styles end*/


/*Intro styles start*/

.intro {
  /*min-height: 100vh;*/
  min-height: 944px;
  background: #0C0B0B;
  padding-top: 250px;
}

.intro_main {
  padding-left: 50px;
}

.intro_title {
  display: block;
  position: relative;
  letter-spacing: -2px;
  color: black;
  -webkit-text-stroke-width: 2px;
  -webkit-text-stroke-color: #FFFFFF;
  font-weight: 900;
  font-size: 150px;
  font-family: 'Roboto';
  min-height: 132px;
}

.intro_title_bottom {
  display: block;
  font-family: 'Roboto';
  font-weight: 900;
  max-width: 1028px;
  font-size: 146px;
  line-height: 154px;
  letter-spacing: 2px;
  color: #FAFAF9;
  border: 1px solid #000000;
}

.intro_sub_title {
  display: block;
  margin-top: 66px;
  min-width: 587px;
  font-weight: 400;
  font-size: 20px;
  line-height: 24px;
  letter-spacing: 0.5px;
  color: rgba(239, 237, 232, 0.65);
}

.intro_title span {
  opacity: 0;
  animation-delay: 1.4s;
  display: block;
  animation: textAnimate 1.5s cubic-bezier(1, 1, 0, 0) forwards;
}

@keyframes textAnimate {
  0% {
    transform: translateY(-100px);
    opacity: 0;
  }
  50% {
    transform: translateY(-50px);
    opacity: 0.5;
  }
  100% {
    transform: translateY(0);
    opacity: 1;
  }
}

.intro_title_bottom span {
  opacity: 0;
  animation-delay: 0.7s;
  display: block;
  animation: textAnimate_bot 1.5s cubic-bezier(1, 1, 0, 0) forwards;
}

@keyframes textAnimate_bot {
  0% {
    transform: translateY(-200px);
    opacity: 0;
  }
  50% {
    transform: translateY(-100px);
    opacity: 0.5;
  }
  100% {
    transform: translateY(0);
    opacity: 1;
  }
}

.btn-5 {
  margin-top: 54px;
  padding: 24px 74px;
  font-size: 26px;
  line-height: 42px;
  border: none;
  background: #E6533C;
  ;
  background: linear-gradient(0deg, rgba(255, 27, 0, 1) 0%, rgba(251, 75, 2, 1) 100%);
}

.btn-5:hover {
  color: #f0094a;
  background: transparent;
  box-shadow: none;
}

.btn-5:before,
.btn-5:after {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  height: 2px;
  width: 0;
  background: #f0094a;
  box-shadow: -1px -1px 5px 0px #fff, 7px 7px 20px 0px #0003, 4px 4px 5px 0px #0002;
  transition: 400ms ease all;
}

.btn-5:after {
  right: inherit;
  top: inherit;
  left: 0;
  bottom: 0;
}

.btn-5:hover:before,
.btn-5:hover:after {
  width: 100%;
  transition: 800ms ease all;
}

.foto_trener {
  position: absolute;
  margin-left: 904px;
  top: 0;
  right: 0;
  z-index: 1;
  margin-top: 167px;
}

.foto_trener img {
  opacity: 0;
  animation-delay: 0.7s;
  animation: foto_trenerAnimation 1.5s cubic-bezier(0, 0, 1, 1) forwards;
}

@keyframes foto_trenerAnimation {
  0% {
    transform: translateX(-200px);
    opacity: 0;
  }
  50% {
    transform: translateX(-100px);
    opacity: 0.5;
  }
  100% {
    transform: translateX(0);
    opacity: 1;
  }
}


/*Intro styles end*/

HTML
=========

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Personalny Trener</title>
  <link rel="stylesheet" type="text/css" href="./css/reset.css">
  <link rel="stylesheet" type="text/css" href="./css/style.css">
</head>

<body>
  <!--Header starts-->
  <header class="header">
    <div class="wrapper">
      <div class="header_wrapper">
        <div class="header_logo">
          <a href="/" class="header_logo-link">
            <img src="./img/svg/AM-logo.svg" alt="Personalny Trener" class="header_logo-pic">
          </a>
        </div>

        <nav class="header_nav">
          <ul class="header_list">
            <li class="header_item">
              <a href="#!" class="header_link">PROGRAMS</a>
            </li>
            <li class="header_item">
              <a href="#!" class="header_link">HEALTHY LIVING</a>
            </li>
            <li class="header_item">
              <a href="#!" class="header_link">COMMUNITY</a>
            </li>
            <li class="header_item">
              <a href="#!" class="header_link">ABOUT</a>
            </li>
            <li class="header_item">
              <a href="#!" class="header_link">STORE</a>
            </li>
          </ul>
        </nav>
      </div>
    </div>
  </header>
  <!--Header end-->

  <main class="main">
    <!--Intro start-->
    <section class="intro">
      <div class="wrapper">
        <div class="intro_main">
          <div class="foto_trener">
            <img src="./img/trener.png">
          </div>
          <h1 class="intro_title">
            <span>PERSONALNY<br></span>
          </h1>
          <h2 class="intro_title_bottom">
            <span>TRENER</span>
          </h2>

          <div class="intro_sub_title">
            <p>
              Programs offer day-to-day Lorem Ipsum is simply<br> dummy text of the printing and typesetting industry.
            </p>
          </div>

          <button class="custom-btn btn-5">
                            <p>PROGRAMS</p>
                        </button>
        </div>
      </div>
    </section>
    <!--Intro end-->
  </main>

</html>