I'm 22no health problems. I'm feeling a warm sensation on the front of my left thigh it comes n goes. No swollen, redness, or much pain.! What could b?

Need to examine. It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. However what you described does not sound serious and you could wait and watch. If you are even slightly overweight try to reduce your weight through diet and exercise.