Check the shutter speed
Indoor photography usually requires a much longer exposure time than outdoor photography, and it’s easy to not notice when the shutter speed has become too slow to get sharp handheld shots. One way to avoid this is to increase the ISO – or use Auto ISO, and let the camera push and pull the ISO according to the light. Using a stabilised lens or camera helps, but a tripod will give you even more options.
A three-stop difference
The details above were taken from images shot at f/2.8. At ISO 100, the exposure of 1/10 sec was too slow to record sharp details. Pushing the ISO three stops to ISO 800 gave the required faster exposure.