I agree with Dominic. Making him feel safe is best way to combat this. Let him know your there and then ease out once he’s dropped fully.
Regular routine always helps too. Try keep the lighting low after dinner, bath routine teeth then bed with stories.
We’re having issue with waking in mid of night and not wanting to go back without one of us there. Which just sprung out the blue (3 yr old) so think it comes and go with phases.
Prob a lot to do with developing imagination perhaps