Have you pressed the mic button accidentally when plugging in the headphones?
Please try to restore the Google app to default settings.
( settings > apps & notifications > see all apps >Google > storage & memory >clear storage & cache)
Please to check there's debris stuck in the jack.
Also, I suggest you can use another headset for a check.
Thanks for your kindly reply.
Could you help me to use the stock earphone for a check?
Please also check this matter under safe mode.
In safe mode, only the factory pre-installed applications will be loaded.
For instructions, please refer to the link below:
If this problem still appears, please kindly let me know. Thank you.