Also called "squirting". I'm now 39 but only discovered my g spot when I was 37. For me it was a progression.
First it was masterful fingers via a determined partner and a willingness to try. Then it happened one time during vaginal intercourse, but only in one position (on my side). Then it happened when he took me doggie style, and more recently missionary. I only just discovered how to give myself a gspot orgasm via my fingers.
My spot is off-centre (a common occurrence) slightly to my right side (which explains why I could never find it before).
The other night I graduated to a new level however; I squirted solely without any physical contact whatsoever. I was highly aroused and had squirted previously the same evening. As I was laying on my side I spread myself open (hand only on my ass cheek) as if to "present all my privates" and it just let go, twice, hard.
I attribute that freak event to already being highly stimulated, having a few glasses of red wine ( relaxes me), being very well hydrated (taking water in all night), and the most vital element....
Drop sheets (plastic) lining my bed with a sheet over. I am always concerned about making a mess, but with drop sheets I could eliminate that concern. It also helps to have an encouraging partner.
It's incredible & highly recommend not giving up on it.
-A