[oxixernibioge]

If you sit quietly, you will notice that all the sense doors are firing all the time. That means sight, sound, sense, taste, smell and mind. Everything is changing all the time. This living organism doesn't stop changing. Of course thoughts will bubble along, just as sensations will dance across the skin, dots of color will splay across the visual field, tones will ring distantly in the auditory field. Usually we just ignore these phenomena, because we're so used to them after being so close to them all our life. We filter them right out. Same with most random thoughts.

Where do they come from, all these sense contacts? It's just part of having a body, being alive. Where do random muscle twitches come from? Where does hunger originate? You could ask those things as easily as you could ask about the origin of random thoughts. It doesn't do any good to identify with any of it too closely. You are not your random thoughts. Don't worry about thoughts.