Is the bias of the accelerometer MPU9250/6000 significantly high?
This is critical datasheet stuff, so you can expect to find it there -- to the point where, if it's not in the datasheet, I would genenerally just not buy the part.
Normally the datasheet parameter you'd look for would be &quot;bias&quot;.  This one chooses to call it &quot;Zero-G Initial Calibration Tolerance&quot;, and it's \$\pm 60 \mathrm{mg}\$ for the X and Y axes, and \$\pm 80 \mathrm{mg}\$.
You're way over that, so you have some other problem.
Note that the specifications are for the chip at 25C -- they also give a &quot;Zero-G Level Change vs. Temperature&quot; at \$\pm 1.5 \mathrm{mg / ^\circ C}\$.  This is no surprise, accelerometers are always drifty with temperature, and little silicon MEMS accelerometers are the worst of the lot.  So if you're going to use this thing, you can predict how much worse you can expect it to be at the temperature extremes than at room temperature.