to get more sodium, would it be good to just add some tablespoons of salt to my protein shake??
Tablespoons? God no. Try a teaspoon.
That would make me hurl in a protein shake!
Why not just sprinkle some on your veg (which you should be getting plenty of each day I hope?).
I add a little salt over my veg and generally cooking through the summer months to help replace electrolytes lost through extra sweating in the hot season.