Examine the obvious damage and wear on the seat belts, buckles, latch plates and guide loops. Make sure that the seat belt reminder light is on when the ignition key goes to the Run or Start position. The seat belts have a lock up mechanism in case of sudden stop or impact in the course of driving, though gives free movement in normal driving condition; ensure that retractors of the belt move back to your chest during driving and reel the belt back to full length when the buckle is undone. In case some of the checks indicate the problem with the seat belt system, change the parts when needed.