Woke up with numbness on one side of my body. possible causes?

Numbness : If numbness involves face, arm, torso and leg of one side the problem could be at the brain level, perhaps thalamus , an area of the brain in charge of sensorial processing. If abrupt onset while asleep, may suggest a small vascular insult or stroke. A demyelinating disorder like multiple sclerosis may produce similar presentation. The best way to identify this is by an urgent evaluation & mri.