DD is 1 and she still does this occasionally, I think it is common (but I'm no expert)
do you wind him properly after feeding? even bf babies will swallow air, so make sure you burp him, even if he's falling asleep after a feed!
imagine a 2l bottle of fizzy drink, full of bubbles stuck to the side.
if you stroke the bottle not much will happen.
now tap the bottle and you'll see hundreds of tiny bubbles moving upwards.
you have to tap baby's back to release the little air bubbles too.
put your palm on his back, just above the nappy line (you don't want to tap the lower back).
then you go up-up-up as you tap-tap-tap - all the way up.
you need to be firm, use the same strength as you would do to clap your hands
keep repeating this tap-tap-tap until he burps even if it takes 10 mins - you'll be rewarded with a luscious burp and a calm baby!
(I used to sign nursery rhymes in my head and tap to the rhythm to stay awake at night! the grand old duke of York is particularly good, one set of taps for each line.)
you can stroke his back in between taps to calm him if he's grouchy, but the taps will do the work
I actually do this every time I pick up a crying baby, especially if they wake up crying shortly after they fell asleep (10-30 mins depending on age).
it is surprising how often they will "respond" with a burp, and I'm sure it is sooo much better for them to burp it out, then ending up with cramps &pain as the air bubbles travel down the gut.
I hope this helps