avoir des fourmis dans les jambes

To feel a tingling, restless urge to move

Describes that prickly, restless feeling in your legs, often from sitting or standing still too long, that makes you want to get up and move.

Après deux heures de réunion, j'avais des fourmis dans les jambes.

After a two-hour meeting, my legs were tingling with pins and needles.

The 'ants' capture that itchy, crawling sensation in a leg that's gone to sleep, and the instinctive urge to shake it off by moving.