Hyundai accent 1.3 1999 "T" reg engine noises
 

recently noticed my accent started making a rattling sound when started,
lasted all of 3 seconds then dissapeared. Decided to have it serviced and
have the cam belt replaced and it was better for about a week. Now ive
noticed it has come back and sometimes lasts longer i.e 20/30 seconds,
doesnt happen everytime you start it though and doesnt matter if its hot
or cold. any ideas?