Cat naps & failed to self sooth

my baby is almost 6 months. And naps has been horrible- it takes 20-40 naps average like 30 mins. 1.5 total of 3 naps on average. I have tried to do all the routine, such as pull down the black out, white noise , mobile music, rock him for 5-10 mins, put him to crib (sometimes even he fall asleep