synonym for child-like [adult]

There is a specific term, and it keeps evading me, that refers to an adult who still embraces child-like wonder, curiosity, etc....

Not inferring a child-like or infantile adult, i.e. someone with a disorder.

I believe it begins with "N". Anyone who may know, your input would greatly be appreciated.

Solution 1:

Naive is probably the term you are looking for:

• Lacking worldly experience and understanding, especially:
• Simple and guileless; artless: a child with a naive charm.

The Free Dictionary

Solution 2:

Jejune

Jejune [adjective]
Naive, simplistic, and superficial: (Oxford)

Ludic

Free spirit

“I like to be a free spirit. Some don't like that, but that's the way I am.” ― Diana Princess of Wales

irresponsible

Uncommitted