My nearly 7mo is a crap napper and sleeper.
He wakes after 20-23 minutes and if I'm there the actual instant he starts twitching I can sometimes resettle for another 20m but I also have a 2yo so usually I can only get to him after he starts crying by which time he's wide awake.
He sleeps 3 x 20 minute naps each day either in cot, car or pram. Is better at night but wakes at least twice for feeds then we have to
Resettle after 20m. Clearly his sleep cycle is only 20m, his brother's was 45m which I thought was bad enough.
Separately he is unable to settle himself without crying but is getting a bit better the more times I leave him.
It's tough though because he doesn't want to be cuddled/rocked to sleep, yet is happy to be cuddled up to me in bed 
Any ideas ladies or will he definitely grow out of this...am sick of listening to mums saying their babies sleep for
3h naps!
On the plus side he is a relatively happy baby during the day despite crap naps, only grizzles when settling for his nap and immediately after waking (as if to say he wanted to sleep for longer)