I'm three, yet each part's the same; in the end I'm only one.
Made of three identical Oxygen atoms, and the word's suffix is "one" (Thanks @Chris Cudmore for the wordplay)
I surround & protect all life on Earth, even those who still worship the Sun.
The Ozone Layer protects the Earth from the Sun's harmful radiation
In the heavens I am holy, I'm sure you've heard of the notion,
Referring to the notion of a hole (holy) in the Ozone Layer
So the people of my beginning have to use quite a lot of lotion.
To prevent sunburn, people apply sun-tan lotion, particularly those from Oz(one), i.e. Australia. (Thanks to @osdavison for the Australian connection)
Maia-who am I?
This is a reference to a repeating lyric in the song Dragostea Din Tei by Moldovan group O-Zone, which spawned the ancient (14 years old!) meme Numa Numa. (Thanks to @El-Guest for spotting this)