Hi,
My son is 16 weeks and has just finally started to take longer naps. He has always been a terrible napper and would literally be awake all day if he wanted to. He would sleep so good at night 7-7pm without any waking. We had many days of 2 or 3 40 minute naps and he couldn't get past the sleep cycle and would just scream. Nothing really worked except time. Just in the last few weeks he has started to take a long 2-3 hour morning nap but he still catnaps (2 * 40 minutes) in the afternoon. I've also read where it can take 3-6 months for them to figure out their day sleep and the morning nap is usually the nap that develops first. I know every baby is different but what seemed to work for us was continuely putting him down clam and drowsy but still AWAKE (no more rocking him to sleep). This has taught him to fall alseep on his own. When he wakes up from the 40 minute sleep cycle we ALWAYS give him the oppotunity to resettle (usually 10-15 minutes) before we go get him. Try not to stress so much about it, there are loads and loads of us that have this problem. The ability to transition from sleep cycles will come with time and maturity!!! Hang in there!!!!!
Trisha