2003 Hyundai Elantra - Knocking then won't restart

engine knocking sound starting up running few 15 s. . can’t start it again nothing happen

What do you mean by that? Running for 15 seconds?? Now it won’t start? Won’t crank? The engine may have just broken but you haven’t given us any info about your car except it is a 2003 Elantra so this is a guess.