Excellent description! One medical term for something like this is "fasciculation". This is tiny muscle spasms and it is very difficult to get a definitive cause for them...theory's range from increased anxiety to over activity. This is usually benign and nothing to really worry about.
Another possibility is that it is just a blood vessel spasm. Again, nothing to worry about in your breast and cause is difficult to determine since they come and go.
Another possibility is a blocked milk duct and the spasm is happening because the tiny muscles around the duct are working overtime to push through.
I had this happen years ago and was never told a cause. (I had a bilateral mastectomy for severe fibrocystic disease with severe pain all the time.) I am in no way suggesting that you have what I did. The treatment for fibrocystic disease is generally not mastectomy, but after YEARS of pain with my severe case and strong family history of breast cancer, if I did have cancer, they wouldn't be able to diagnose it because my entire breasts were so cluttered with cysts.
Even now, after 7 years of having them removed, I will still get that buzzing and sometimes itching feeling INSIDE one of my implants. How weird is that? Phantom sensations I guess.
It it really starts to bother you, go see your doctor. They could do a breast ultrasound to rule out any obstructions or growths.