I have had my Mavic Air for about 18 months and it has performed flawlessly for me the whole time.  However, on a recent flight, I noticed that when it is in the air, it starts turning in different directions without me touching the sticks. I can still control it and bring it back but the turning left and right without me doing anything is annoying.  I haven't calibrated the IMU since I bought it.  Do you think recalibrating the IMU would solve my problem.

Hi. Thank you for reaching out to DJI Forum with your inquiry. It is recommended that we do the IMU Calibration for your DJI Mavic Air so that it will optimize performance of the said drone and also please do a Compass Calibration to ensure that your drone will not drift while it hovers. I will be posting an official DJI Tutorial Video for the IMU calibration for the drone. For further inquiry please feel free to post it here at DJI Forum. Thank you.

Really easy to do and will most likely fix your issue.