If he hasn't shed since you got him then it is possible he is coming up to a shed, depending on how long you've had him you should have left him pretty much alone for a week or two to settle in.
the typical signs of an upcoming slough are that the skin will look dull and sometimes darker on some species, and if you handle them (NOT generally recommended) their skin will feel dry and a little loose, and their eyes will go cloudy for a few days and then clear up, its normally about 4 - 5 days later you will find a skin in the cage. Keep in mind that most snakes like to hide while in slough because their sight is severely affected they feel vunerable, so if he goes into hiding and you try and grab him out you could get bitten.
leave him alone for a week and see what happens.
how long have you had him and how old is he ?