I suppose you connect from non-schengen to schengen countries when connecting from 4S to 4, correct? You didn't mentioned your origin/destination.
But you will be fine, if it's on one ticket, which I suppose. Your bags will be checked through (customs will be done at your final destination within Schengen), and boarding pass for onward flight already issued.
When landing at 4S, which is basically a long and modern building, you would have a segregated walkway down to the center of that building, and you clear immigration there (there is a transfer desk there too, just in case you missed your flight for rebooking or if you need to get your onward boarding pass, which I don't expect since you are IB to IB and it will be already issued). There are also automated passport control booths, but not sure if it is restricted to Schengen nationalities only.
Once you have passed immigration, you will walk down a few levels and an automated train will take you to 4. I remember it took 5-10 minutes. Once you are there, follow connecting signs and you will need to reclear security. There is a IB lounge available there.