It normal. Digital servos are constantly checking and adjusting the output positon. Note that digital servos certainly use more current than analog servos and that they will cost you 5-10 sec of run time if you run Mod sedan or 1/12th scale.
What I run: Schumacher Mi5/Associated RC10R5.1/Associated RC12R5.2/Futaba/HobbyWing/Team EA Motorsports/BSR Racing
Where I run: Florida Indoor R/C Complex/Thunder Racing/Florida On Road State Series