Like any broadcast, there may be areas of weak signal that may cause poor reception. You can try relocating the radio to another part of the room and adjusting the aerial to try and improve the signal.
Where aerials are a pigtail wire version rather than a telescopic style, ensure they are completely unwound and straight.
Putting the DAB radio close to a window can help, and reception may be better upstairs rather than downstairs.
You can also check DAB coverage in your area by visiting Digital Radio UK's Postcode Checker
* The postcode checker provides predictive DAB coverage information, and allows you to check which digital stations should be available at your address. It doesn't allow for other factors that may affect reception, such as whether you live in a very built-up area, or in a basement flat, if the building has a steel frame or is made of reinforced concrete.