Union members working at the Driver and Vehicle Licensing Agency in Swansea have begun a four-day industrial action due to health concerns over coronavirus.
The PCS union said it has asked its 3,300 members at the DVLA - almost half the agency's total workforce at Swansea - to strike "to protect workers' safety" because more than 2,000 staff each day are still going into its offices.
The DVLA said the strikes may cause delays to calls into its contact centre and to paper applications it receives.
Online services will still be available.
The union said progress had been made in talks, with the DVLA agreeing to revise risk assessments and remove more than 300 desks, but a lack of immediate steps to reduce the on-site workforce has led to the ballot and walk out.
"They (staff) don't feel the DVLA are taking their health and safety seriously," the union branch secretary for the DVLA Sarah Evans told the BBC.
The PCS said more than 500 DVLA workers have contracted coronavirus since the pandemic began, leading to the Welsh Government raising concerns about the workplace.
The DVLA told the BBC it has had no new confirmed COVID cases since March 24 and it has consistently worked with health agencies to introduce a wide range of safety measures.
"The safety of our staff is paramount and we have continuously adapted our measures," said its spokesman.
In December the National Franchised Dealer Association urged its members to promote the online services of the DVLA after user research found its speed and convenience were real benefits and 52% of motorists would likely sell their car to a dealer who completed the administration for them.