Anyone else?

My 13 month old has recently started waking up at 5 am instead of his usual 7/7.30 am. He has also started being fussy at nap times. I usually rock him in my arms with lullabies playing and wait till he’s settled and then put him down in his cot and he falls asleep. Only recently, he arches his back and cry’s when I try to rock him so I put him straight down and leave and he starts to cry again. Sometimes he settles and falls asleep but other times he doesn’t. He sometimes cries so hard that I can’t leave him by himself. He does this with both naps. I don’t know where it has all come from as it all happened just out of the blue. Anyone else had this problem and know what it is?