Starting problems
When I restart my Macbook Air, a question mark appears on the screen
MacBook Air 13″, macOS 10.15
Question marked as
Best reply
Hi,
It means your MacBook Air can't find the macOS to boot. Resetting NVRAM could solve the issue.
Reset NVRAM or PRAM on your Mac - Apple Support
If it doesn't help, you'd better make Genius Bar reservation if your local retail Apple Store is open or find opened local Apple Authorized Service Provider to be examined your MacBook Air.
Genius Bar Reservation and Apple Support Options - Apple
Apple - Find Locations - Location Selector
Also following document could help your issue.
If your Mac starts up to a question mark - Apple Support