Does he get enough exercise during the day?
If we don't exercise our dog during the day, she'll get up during the night and be completely restless and impossible.
We have a spaniel - she's from a show line, so doesn't have as much energy as a proper hunting dog, but she needs 3-4 walks daily (morning, afternoon, early evening and just before bedtime) as well as a minimum of 30 mins of fetching/running in fields/playing with other dogs. On top of that, she needs mental exercise where she gets to use her nose and head, so mental exercise toys (such as Kong Genius, Kong Wobbler, Buster Cube and other treat dispensing toys).
The fetching can cause some dogs to get stressed if overdone, but if done for a limited amount of time, it tires the dog out. But mental training is also needed to make the dog happy and tired.
A simple mental exercise thing is to spread the dog's food in the garden, then let the dog find it all himself. Doing that with our dog makes her sleep like a baby.
It could also be that there are some new noises outside that he's reacting to - birds, cats, foxes. My friend had that problem with her dog and if she pulls the blinds down, it helps.
Having the dog sleep in one room, such as the kitchen can also help - just make sure the dog has access to water during the night.