Four naps a day sounds about right at this age . Oh how I hate those 40-45 minute, one sleep cycle sleeps! All my kids did it.

I was able to get through it with DS1 by bouncing him in his hammock as he stirred and he would go back to sleep.

With DS2 I would sneak into his room a couple of minutes before 40 mins was up and as soon as he stirred (he would sigh and move his head), I would pat his tummy and he would fall back to sleep (it used to work for at least one of his naps each day).

With DD (who is of course bub #3) I just gave up and went with it LOL! I didn't have time to stress out about it and try and resettle her. Funnily enough it was much more relaxing when I finally just gave up on it all .

They all eventually learned to sleep past 40 mins

Good luck today