Burning feeling on right leg, 3 days increasing in frequency. sometimes all or part of leg; burn comes and goes. no pain. when should i be concerned?

Nerve compression: Sciatic nerve compression will cause those symptoms as will vascular issues,although the vascular would probably already have caused a much more major problem by now. Get it checked out before it is there continuously

Neuropathy: Hi, You might have Peripheral neuropathy, an inflamed nerve, there are too many reasons for that but in you case it could be due to repetitive physical stress, such as repeating the same movement for long periods of time, other risk factors are Diabetes, Alcohol, Vitamin b12 deficiency, Infection, exposure to toxins, disk problem, Kidney, Liver or Thyroid disease. See your MD if not better soon.