“100%” Cotton shirts that feel like plastic

over the last 1-2 years I’ve noticed shirts will be labeled 100% cotton but then when I wear them it feels like theres plastic in it. I can tell somethings up because I get hotter and sweat more in plastic shirts than I do in cotton. The shirts also don’t wrinkle or stretch out which along with the unbreathability seems very uncotton-y to me 😅 is it the way the cottons being processed? Would love to know if anyone has an answer to this and maybe anyway to find out if future shirts will have this issue before purchasing?