Thanks for writing in
There are number of regions for numbness
. Lot depends on your age and associated factors. Some of the reasons are:
1. Cervical Spondylosis: X-ray Cervical spine
is needed to rule out that.
2. Neurological defect
3. Muscular weakness
4. Vascular disease
You need to be checked by your physician and need some investigation done to get to a diagnosis. Most probably this is due to cervical spondylosis. Proper exercise and precautions will get rid from that.
Best Wishes and get well soon