Short Naps for 3 Month Old

Now is when you have to teach him how to put himself to sleep, and help the naps to consolidate. One trick that might work: 5 minutes before he usually wakes from a nap, go in, make a little noise, enough to get him to roll over, not wake up. It should reset his sleep cycle.

Also, make sure he is ASLEEP within 2 hours of waking, so start getting him ready for his nap after he has been up for 1.5 hours. You have to find the sleep window.

He keeps waking because he can't self-sooth, so after each sleep cycle, he wakes up. The nature of baby sleep changes at 12 weeks and becomes more "adult like," so babies don't just fall asleep anywhere, etc. they have to learn how to sleep. Make sure you are putting him to sleep AWAKE. When he pops awake after being put down, start over, nurse until he is relaxed and keep trying to put him down until he finally puts himself to sleep. It takes time and a lot of work, but in a few weeks, he should have the skills and he should be sleeping better.

My DD was doing the same thing. She would wake up from her naps and wouldn't go back to sleep... Especially if she was in her crib. I started putting her in her bouncy chair right when she woke up, giving her a blanket and her lovey, a binkie, turn on the music and vibrator to the chair, and bounce her till she fell back asleep. She would usually sleep another 30 minutes to another hour!!! :)

Have you tried swaddling him? He's still very young, and it may soothe him. Good luck.

Well he should be napping during the day.
Is the place he sleeps for naps the same as for his all night sleep?
We used a cradle for the first 5 months then used a pack n play for naps while the crib was only for bedtime sleep.
A) Make sure he's getting enough to eat esp during the day.
B) Can you take him for a walk in a stroller or a drive to help him fall asleep?
C) If he's not getting enough to eat, you may need to supplement.
D) Is he teething during the day?
E) Is his brother waking him up form his naps
He's probably cranky during the day due to being over tired.
He probably goes right to sleep at night because he's so tired.

So basically I would ensure he's getting enough to eat, isn't teething (if so I'd give some infant tylenol) and make sure brother isn't waking him up.
Hope that helps