My 1999 gmc sub. has on at least 3 ocassions

my 1999 gmc sub. has on at least 3 ocassions refused to start. 1st i thought the battery was dead, it needed replacing anyway so i did. along with that the surpintine belt was replaced as well. then all of a sudden it would act as if the battery was dead. would not even act as if it would want to turn over. then it would. very hessitant and slugglish. i had this same problem sith a kia and it turned out to be the starter relay, could this be true of this car as well?