See my custom entity as a normal page in drupal 8
Then you have probably defined an admin path to view the entity:

/src/Entity/MyEntity.php

 *   links = {
 *     "canonical" = "/admin/structure/my_entity/{my_entity}",


Change this to a non admin path:

 *   links = {
 *     "canonical" = "/my_entity/{my_entity}",