L.C.
If 30-45 minutes is all he's sleeping, it's probably a single sleep cycle, and likely all he needs.
It may be that the first nap is too close to waking after the night, and the second nap is too far away from the first one.
Babies' sleep needs --like adults'-- change from day to day based on variable factors like current growth speed, what the immune system has encountered and energy expenditure, including thinking time.
It's slightly easier to avoid going crazy by following the baby's cues in terms of sleep needs: you can see when he's tired, until then he won't happily nap, and after that point he'll be getting overtired and stressed. Watch him daily and expect the needs to shift a bit each day. There is nothing in a baby's body that comes prepared for the existence of clocks, so clocks don't need to determine when he's tired (or finished sleeping).