RepairPal Certified shops can diagnose and repair your 1998 Chevrolet C3500. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Gas or Diesel engine sounds like you might have a injector acting up. Maybe just dirty try a good injector cleaner and a tank of premium fuel first. Also get it scanned for codes there may be one that is pending and hasn't set yet.