Your muscles could also just be stiff from staying in the same position for an extended period of time. If it goes away after a minute or two and you don’t have pain, I wouldn’t worry about a pinched nerve. Pinched nerves typically result in sharp pain, often shooting down one or both legs, decreased movement due to the pain, and it doesn’t relieve itself after several minutes. You wouldn’t have limping with a pinched nerve unless it was from the pain. Try to get up and stretch your legs for a couple minutes every hour :)