My DD is 3.5 months, she had been taking great naps until she got to about 2.5 months, that's when it all fell apart. I'm not sure what happened exactly, but I tried so many different things! I tried shh-pat to get her back to sleep, wake to sleep, holding through the jolts, nothing worked. For a while, if I held her her entire naptime, she would go back to sleep after the 45 minute mark after a few minutes of being awake and me rocking her. In the process of trying to figure out her naps though, she got to be a much better self soother
Her previous bedtime (to be asleep in bed) was 7:30 ish, sometimes a bit earlier or later depending on how the day went. She at first woke up twice a night for a feeding, then went to three times at about 3 months (I assumed growth spurt), then she was waking early for the day, and started waking every hour from about 5:00 on. Most days, I ended up holding her in the morning until what had been her wakeup time. Her record of night wakings was 7 in one night... Sigh, very little sleep for me. THEN, yesterday I put her in bed after her bedtime routine at 8:45, she stopped making her little baby falling asleep noises by 9, so I am assuming she was out around 9. Tonight, I put her down around 8:35, and she was again out around 9 (assumption, since she was in there alone and I don't have a video monitor). Last night, was AMAZING! She slept until 4:30am and woke to eat, then went right back to sleep until 7:50. I am hoping that she will do a repeat of this tonight, but we will see.
Anyhow, after this wonderful night, she woke up smiling and happy, played for a while (not sure how long, DH played with her this morning while I napped... I couldn't sleep because I was so anxious about DD not needing to eat during the night, silly, I know) Then, she took an 1.5 hr nap. Later, she played about an hour and 45 minutes, then took a 2 hour nap! We were out and about running errands after that, so it is hard to say how long she actually napped, but she did in the car.
It wasn't a drastic change in bedtime, but it made a huge difference all around. Also, admittedly, this is a new thing, and I don't know how she will do tomorrow, but this was the only thing I changed, and the next day was immediately better, so I tend to think that was the reason.