Why doesnt my cat want to be held?

i love holding my cat, he is soft and is like a big snuggle ball to me...but i only get to snuggle for a couple of seconds then he struggles to get away. i have had him for about two years now and moves if i lay next to him or hold him..he is very relaxed and never hides so i know hes not scared. what should i do and how can i get him to let me hold him?