My girl is almost 22 weeks old and, in my opinion, is a pretty good sleeper. She will fall asleep at around 8/9pm and sleep until 5/6am, wake up for a feed and then usually go back down until 8ish, although sometimes she will be awake again at 7am. She has slept like this since eight weeks old, so I know we are very lucky in this regard! She also sleeps pretty well during the day, 3/4 naps normally lasting 45 minutes to an hour (although sometimes she’ll have more, shorter naps or fewer, longer naps).
However, she needs to be rocked/bounced to sleep every time, including day time naps. She doesn’t like dummies, has spat out or flatly refused every one we’ve tried. I’ve also tried putting her down whilst drowsy and that is hit or miss, sometimes she will fidget for a bit and then fall asleep, or she will jolt awake and either start crying or just lay there chatting away!
Just recently she has started chewing/sucking on her hands when she’s tired, and sometimes she will wake up in the middle of the night, whinge for about 30 seconds and then fall back to sleep, so perhaps she is already learning to self soothe?
Again, when she does fall asleep she sleeps well, but it normally takes a good 10 minutes of gentle bouncing and shushing/white noise to get her to fall asleep. Rocking the tiny 6lb newborn she used to be is much kinder on the arms than bouncing the 16lb nearly five month old that she has become! 
Is self soothing something they learn on their own or should I try and encourage her to start? I got a lot of ‘rod for your own back’ comments when I started rocking/bouncing her to sleep, but the 8/9 hours of sleep she does after said bouncing/rocking is worth it! I just don’t want to be bouncing a toddler to sleep on my lap in the future! 
When did your children start self soothing? Is it something they did on their own or did you have to encourage them to learn?
Thanks 