HELP! My child WILL NOT stay asleep after I lay him down!

My son will be 4 months old tomorrow. He will not stay asleep once I lay him down for naps. He will only sleep in his swing or while being held. He sleeps AMAZINGLY through the night(10-12hrs.)!! 😍😍😍 but he won't nap by himself during the day. He naps regularly every couple of hours (10mins-1hr.). But I've read that his naps should be 1.5-2hrs long. Any tips to help get this boy to nap?