My son has been a great napper since we started sleep training around 2 months. Usually 2, 2 hour naps and 1, 30-40 min nap. Since last week, he will only nap for 30 min at a time. His first nap is usually around an hour, if we are lucky and then the rest are just terrible. By mid-late day he is just a bear because hes so tired, but he just. wont. nap. His awake time is usually no more than 2 hours. We have always watched for sleep cues, and still do. We havent changed anything to his routine other than adding baby food (along with an oz or 2 of formula) to his afternoon feeding. What the heck is going on!? Its driving my husband and I crazy.
Re: My 6-month-old suddenly doesn't want to take his naps!
Beyond that, babies just change over time and there isn't really any cause. Their nap schedule won't stay the same forever. Sometimes my daughter will be thrown off for a bit and then go back to how she was. Fwiw, at some point around the 5-6 month mark is when my daughter switched from three to two naps a day.