MTG

"Whenever a creature enters the battlefield" is just a more general version of "When ~ enters the battlefield", so yes even in this case it'd trigger its own ETB. This is the relevant rule, which even calls out this case:

603.6a Enters-the-battlefield abilities trigger when a permanent enters the battlefield. These are written, “When [this object] enters the battlefield, . . . “ or “Whenever a [type] enters the battlefield, . . .” Each time an event puts one or more permanents onto the battlefield, all permanents on the battlefield (including the newcomers) are checked for any enters-the-battlefield triggers that match the event.

Cards are generally not worded this way to avoid confusion though. Instead you might see "Whenever ~ or another creature enters the battlefield", for example with [[Thorn Mammoth]].