Brief Answer:
A neurological condition to be considered.

Detailed Answer:
Hello and welcome to "Ask a Doctor " service.

I have read your query and here is my advice.

If this numbness is acute, a transient ischemic stroke may be considered.

Migraine also may cause such numbness if you suffer from it.

In cases of prolonged numbness, the problem may be located in the brain ( brain lesions for example ).

In all the cases, it is necessary an evaluation by a Neurologist in order to understand correctly your condition.

If above mentioned conditions will be excluded, anxiety may be the culprit.

Hope you found the answer helpful.

Let me know if I can assist you further.

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