Paradox Haze targets a player when it's cast, and it enters attached to that player.

If an effect causes the enchanted player to skip their upkeep step, this ability won't trigger.

If two Paradox Hazes enchant the same player, they'll both trigger when that player's first upkeep of the turn begins. The player will get two additional upkeep steps.

If echo triggers during the first upkeep, it won't trigger again during the second upkeep since the creature won't have entered since that player's last upkeep.

Abilities that trigger "at the beginning of [your] upkeep" will trigger at the beginning of each additional upkeep as well.