Hi and welcome,
Tingling and other sensory issues in limbs whilst sitting or laying down are typically situation specific and not usually suggestive of a neurological condition like MS because its more commonly suggestive of the temperary interuption in (blood flow or nerves) circulation, this type of thing could also be warning sign of meralgia paresthetica too with it progressing to a continuous burning sensation.
"Meralgia paresthetica is a condition characterized by tingling, numbness and burning pain in your outer thigh. The cause of meralgia paresthetica is compression of the nerve that supplies sensation to the skin surface of your thigh."
If it's possible i'd get it seen by your family dr, the odds of this type of situation being the first presentation of a neurological condition like MS is very unlikely.
Hope that helps.....JJ