Vietage was launched in July 2020, but was suspended in April last year as the fourth wave of the coronavirus hit the country hard.
The train has six cabins with two seats along the window each to offer passengers views of the green rice fields, mountains and sparkling coastline of central Vietnam.
Tickets for the 323-km (200-mile), six-hour trip cost US$350 and include a complimentary three-course meal, free flow of wine and beer and a head and shoulder massage.
Last year CNN listed Vietage among Asia's six most amazing journeys.
Da Nang gained fame for its long beaches and upscale resorts while Quy Nhon used to be the former seat of the Cham Kingdom and is now an emerging tourist destination with sandy beaches and turquoise waters.