Hi Pam, at 4 months old he needs to be transitioning to a four hour routine, his A time is a little on the low side, should be getting up to 2 hours, i would try extending his A time and moving towards the four hour EASY
usually 30min naps mean OverTired but because he is waking up happy it shows that he is actually having an UnderTired nap, so hes not sleepy enough to have a full sleep because he hasnt been awake long enough.
take a look at this:http://babywhispererforums.com/index.php?topic=63161.0