[user104658]

Not to be insensitive but... are you fat? Or do you sit in "odd" positions?

It sounds like you're putting pressure on the nerves that run into your legs which will numb them (when the feeling starts to come back the nerve ****zes out, that's the cause of pins and needles). However that's not entirely normal UNLESS you're quite heavy, or you're sitting in a strange way that puts pressure on your legs. If it's the latter, it's not dangerous in itself, but I'd suggest finding a better sitting position because sitting with your legs twisted under you or at strange angles will **** up your knees and hips in the long run.

Fun extra story: My legs always go numb when I sit for 1 hour + on the toilet browsing TiBB . It's the way the toilet seat presses the back of the legs. But I quite like the feeling of pins and needles so I let it happen .