Is it true that people who eat too much salt in their diet could sweat less and feel warmer than normal? I've always felt way too warm, and I noticed I consume a lot more sodium than the RDA.

Extra salt. Eating too much salt is very bad for your health especially your blood pressure wheather it keeps you warm or not, it is possible it can make you sweat less because the extra salt retains water in the body, so please for the sake of good health do not use extra salt in your diet. Good luck.