Wiktionary
just wondering
interj. (context informal English) (non-gloss definition: Used to qualify a question or action, explaining it as modivated by curiosity.)
Usage examples of "just wondering".
No, I was just wondering what would happen if we made a feint at that crowd—.
He was just wondering if he should turn around when he caught a glimpse of someone just around a curve ahead.
She was just wondering if she should risk calling him on the comlink when the child spoke again.