Brief Answer:
Possible peripheral neuropathy

Detailed Answer:
I read your question carefully and I understand your concern.

If the symptoms are limited to the leg then a brain issue is unlikely (if the arm and the face are involved that would change things of course). If only on one side a spinal cord issue is unlikely as well. It would be much more likely to be due to peripheral neuropathy, damage to one or more peripheral nerves.

Such damage may be due to several causes like compression on nerve root in the back from disc bulges, compression of more peripheral nerves due to trauma, local muscle spasm and inflammation, arthritis etc.
To be more specific some more info might have been useful such as the distribution of the symptoms (say including the beck and buttocks, inside or outside of the leg, above the knee or below the knee, including or not the foot/fingers etc, which fingers, etc). Also is there any change in skin color, local temperature, swelling, abnormal vessels etc which might indicate other causes like blood vessel or arthritis issues.
Furthermore a physical exam would be necessary for symptoms like altered reflexes, muscle weakness etc which would direct the need and selection of possible tests like nerve conduction studies and imaging.

I remain at your disposal for other questions, possibly with some of the information I mentioned.

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