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
Meralgia parestheticalike supermum said... I had this also was told I sit too much at work n needed to stretch more it got worse over time until I would awake in the night in excruciating burning pain I would even have to check my skin to make sure I didn’t actually have any burns eventually it kept getting worse and to the point it just stopped completely and I probably should’ve listened to the stretching advice because now for the last 11 years I have no feeling in about 8“ x 4“ area on my thigh