hi,
have things gotten any better? i know my ds went all wonky right around 4 months too, and it seemed to be mostly developmental.
i found that trying to soothe during the entire naptime was what helped him get through it best.
course, with #1 running around, i could only really totally devote myself to that during her naptime. otherwise, i would try for about 10 minutes or so & then get him up. he'd just go down for his next nap a little sooner.
HTH