This is correct, this is the noise from the sensor. all sensors have noise, you need to filter them out.
From this page
https://ozzmaker.com/berryimu/
Combining Angles from the Accelerometer and Gyro
Once you have the both the angles from both sensors, you will have to combined them to overcome the gyro drift and the accelerometer noise.
We can do this by using a filter which will trust the gyro for short periods of time and the accelerometer for longer periods of time.
There are two filers you could use, the Kalman Filter or the Complementary Filter. We will used the Complementary filter as it is simple to understand and less CPU intensive. The Kalman filter is way to far complex and would be very processor intensive.
Mark --OzzMaker.com --
