It sounds like he has a little anxiety and as he is very new to you having only done 1 full week of full days I think you need to give him more time to adjust. If he is anxious to begin with then he may take longer to transition too. I'd give him lots of positive reassurance and reinforcement and then if after 4 weeks you see no improvement I would be inclined to just keep a written record of my observations of these anxious behaviours incase it is a sign of bigger things. Chances are he will be fine though. Fingers crossed and good luck