Occasional warm feeling going down the back of my left thigh. feels like warm water going over it. only last for a few seconds. happens a few times ?

Left thigh parathesi: When does it occur after sittings extended periods? stretching/ on waking? May be sicatica equivalent( sciatic nerve compression due to spine) , piriformis syndrome equivalent ( sciatica compression due to muscle) , nerve compression, rarely Lyme, B12 usually lower0 or rarely mass or MS. F/u /w doc on exercise , diet , motrin like products , or gabapentin, as well as diet