I think that reaching out to your existing regulars is a great start- perhaps you could offer them a discount on a future trip if they introduce a new customer to you.
In terms of presence look at your own personal networks (in real life and on line) and let everyone know that you’re back in business and ask them to share far and wide. What has been lovely to see is that we are all supporting local so I think that making sure you’re tapping in to this would be great.
I’m unsure of your location but if you’re in a city consider the local businesses that have now returned to work and may need taxi’s etc, and join your local community pages, facebook pages etc and let them know that you’re available.
Also have a think about how you could pivot what you’re doing. For example I saw a number of articles saying that courier businesses are very busy at the moment. How could you offer a service that could deliver parcels instead of people to their destinations quicker?
Best of luck!