Is It Normal To Feel Numbness In Legs Due To Prolonged Sitting?

Is it normal to have my feet fall asleep after a few minutes of crossing my legs? There have been times when I stand up after sitting and crossing my legs and I can't walk because if I put weight on the foot that fell asleep I will fall. I either can't feel it at all or It feels very weak and sluggish. Sometimes its my leg and sometimes its just the one foot.