I'd say a good lot of sleep disturbances is developmental at this age, the darkness becomes more scary, shadows play on their imaginations. We had lots of leaving the door open, hall light on and eventually agreed on a new red light for his room that stays on all night to shine at the curtains as he wAs scared of the shadows in the curtains.
It did pass but took a while I must say, and we had a reward chart for going to bed nicely and not shouting or messing about and that worked as he liked to collect his stars in the morning x