15 month old up hourly… anxiety?

My 15 month old has always been a terrible sleeper- usually up about 5 time a night but at the moment/ the past 3 days he has been up every hour, on the dot.

I suspect it is separation anxiety because he shouts mum and cries as soon as he’s up, and will fall back asleep when I pick him up and cry when I lay him down…

For some background, he ha 2: naps, 9:30-10:30 and 2/2:30-3/3:15. Then asleep by 8.

I feed him to sleep at nap time but he puts himself to sleep at bedtime.

Does anyone have any advice? If it is separation anxiety, what can I do to help it? I’ve put one of my tops in the cot but not really changed much