Dead left leg comes now and again, lasts around a day, feels like it is coming from my hip, is this a sign of something serious?

Potentially, but: unlikely. Pinching of the sciatic nerve where it exits from the spinal canal and blockage of an artery in your leg are serious problems Less serious (and more common) is when the leg "goes to sleep'" when there's pressure on the sciatic nerve from crossing the legs, sitting on a hard chair or sitting in one position for a long time. Usually a tingling feeling occurs when it wakes up.