Other mommies pointed out - it could be a growth spurt... could be teething, could be the cold. (Although the fact that he doesn't cry is interesting.)
Since he isn't crying, like another mom said I'd let him resettle himself back to sleep. It is an important skill to self soothe and nursing him back to sleep isn't something you want him to depend on. Sometimes we wake up in the middle of the night for no reason, and resettle ourselves back to sleep. Perhaps that is the case here.
If you suspect he's teething, we used Hyland's Teething tablets. They really help the baby be more comfortable and slip back into sleep if toothing pain awakens them. They are homeopathic and you should be able to find them at major chain grocery/drug stores.
Of course, if he's going through a growth spurt, a night nursing may be needed. (He'd "ask" for it in whatever way he normally "asks" to be fed.)
When babies go through developmental milestones... sometimes sleep is effected. (Eating, rolling over, crawling, walking, talking, etc...)
Good luck.
T.