What Leg Injury Is This?

The upper backside of my left thigh is hurting. Not a sharp pain, but a numbing sensation pain whenever I make an initial motion on my leg (usually when I'm sitting down or in bed and move my left leg, the 1st move will hurt) But then the repetitive or continuous motions following that wouldn’t hurt. It doesn’t hurt when I stretch it. When I pound gently on that area with my hands to mage it, it feels better. Is this a muscle strain or hamstring pull? Or something else?