We are sleep training LO who is 4 months and doing checks every 5, 10, and 15 min but I'm wondering when really is the best time to go in for the first check....

LO will start whining softly but then it will turn into loud yells for us which can go on for 30 min. So not what I would consider him crying but it still pretty loud and sounds distressed. Do I go in then for the first check or wait until those yells break down into full out crying?