Lots of discussion at "periodic warm sensation in lower left leg". Try it?
Search this web-community. You will find number of people complaining various type of sensations.There may be many causes or you may not find any thing.
I had burning sensation on my feet in summer and In winter I used to get hot/cold sensation in my spinal column for the last 30 yrs. Now the sensations of tightness in my feet. No diagnosis has been made so far.
This is not serious. But it is better to consult your doctor.