念叨 niàn​dao
mutter verb
to repeat something over and over or harp on a topic; to mumble to oneself

He kept muttering to himself, though I don't know what he was complaining about.

reminisce verb
to talk about someone or something frequently, especially out of longing, concern, or nostalgia

Grandma often talks about going back to visit her hometown.

Frequency

Movie subtitles
0.090 per million appears in 0% of films
Written text
0.164 per million

Sources