3 of 8 added 683 characters in body

MATL, 37 36 bytes

0`Q4\'Loading... 'y'|/-\'w)hD2.5&XxT

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###How it works

0                % Push 0: initial valur of counter
`                % Do...while
  Q4\            %   Increment modulo 4. This avoids overflow
  'Loading... '  %   Push this string
  y              %   Duplicate counter
  '|/-\'         %   Push this string
  w)             %   Swap. Select the character given by the counter
  hD             %   Concatenate the two strings and display
  2.5&Xx         %   Pause for 0.25 seconds and clear screen
  T              %   Push "true". This is used as loop condition, to it
                 %   generates an infinite loop
                 % End implicitly