One time while traveling, I put a baby mattress in the back seat for the baby. During the trip I rested on the mattress with my baby and had a strange sensation about my breathing. The static from the mattress was actually semi-suffocating me.
From that time on I made sure to have a heavy bed pad between the mattress and bed sheet. Poor babies no doubt have the same problem and may or may not be part of the SIDS problem.
This was my personal experience. I wonder how many people put a sheet only over the mattress and then put their baby down for a nap. It has now been over 40 years but I will never forget that breathing sensation. I am sure I had a light pad over the mattress, but, that was not enough.