I have experienced something similar but on the outside of my leg, and it would often turn into a feeling of painful numbness. In my case it was because my pelvis/hip were out of alignment so I had some physio to help sort it out. I understand other back/sciatica problems can involve strange nerve sensations in your legs too, but there are also other conditions that can cause them as well so it might be a good idea to check it out with your doctor.
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