Is it wrong for me (a mother) to sleep naked with my 16 year old son?

Unless you are trying to teach some kind of self resistance to your child, I think it is inappropriate. Two things:

By age 16, the son should be sleeping by himself and not with you.

Even if, you share the bed, why without clothes. Humans have been around for ages and there is a reason that it has been established since centuries that you sleep nude with your companion/ spouse/mate and not with other family members.

Imagine your husband/ boyfriend telling you that his mom slept naked with him when he was 16 years old (not 16 months). How would you feel?

If you can't sleep with clothes on, sleep in your own room.

Source: QUORA