Is it possible/likely to have jhana appear when one is doing mindful/insight meditation, on it's own?

I seem to keep having these experiences where it doesn't seem like I'm all too concentrated (sporadic thoughts here and there), then all of a sudden I'll have this experience of an 'interpreter' disappear and I'm left with this blank experience that is quickly followed by 'a coming back down to earth' and a feeling of intense joy/happiness for a couple of seconds. The longer I seem to stay in this 'blank' the longer those feelings last afterwards.

Any and all thoughts are appreciated

OH! And if this does keep happening (it's happened on 4 different occasions) what should one do? I being the mind back to the sensations because I assume this is what should be happening.

Thanks