Short daytime naps

My 11 week old has suddenly started taking very short naps during the day (30-45min) at a time. I put her down after about 1.5hrs of awake time- swaddle, white noise and pacifier. I know sleep begets sleep so I’m trying to get better night time sleeps by having her nap a little longer during the day. She only sleeps an average of 13 hours in a 24 hour period.

My Ped said it is too early to sleep train and to only start at about 16 weeks, but we are trying to be consistent with timing and get her out of the habit of being rocked to sleep. She is still struggling with this so sometimes she will nap in the rock and play and other times in her bassinet but I have to rock the bassinet slightly to get her to sleep.

At night, her first stretch is anywhere from 4.5 hours to 6 hours, we will feed her and she will go down again for another 3 (ish) hours. She is eating about 4 oz every 3 hours (longer at stretches between feedings at night).

I find when she has good daytime naps she sleeps better at night.

Are these short daytime naps normal at this age? And how do I get her to sleep longer during the day?