You sound very observant, M.. It's fairly common for babies to experience "periodic breathing" and stop breathing for 5-20 seconds at a time. If it runs longer than 20 seconds, it's a stronger concern. Have you actually timed these episodes with a watch? When something anxiety-producing is happening, time can seem much longer that it actually is.
More importantly, does the baby turn blue or go limp while he's doing this? You'd be most likely to notice limpness while he's awake. Pink or even a little purple in the face is considered "normal" during these episodes. If he spontaneously starts breathing again before he turns blue, pediatricians do usually say that's "normal." There's not too much they can check besides taking an X-ray, and usually won't do more invasive testing unless there is clearly a problem with very long episodes or the child turning blue and pulse slowing down.
As a person who is sometimes plagued by central apnea (a failure of the body to breathe itself normally), I've done a great deal of research on this topic over the years. Unless the baby is overweight, or has some structural problem (friends of mine had a baby whose tongue was too big for her mouth for her first two years, and struggled with obstructive apnea), he probably has mild, normal central apnea or periodic breathing.
You might want to make an effort to be sure the air this little guy breathes is free of any perfumes or other chemicals. In my own case, my central apnea is triggered by common chemicals that I inhale. Perfume, air fresheners, fabric softeners, scented candles, and many common household cleaners have toxic ingredients, and I have to stay away from them. If I get exposed, my blood chemistry changes and my body doesn't know when it needs oxygen. I can have these episodes even while awake – I just start feeling woozy and realize I'm not breathing. I can deliberately breathe while awake, but it's impossible to sleep when I get this.