Microphone is not working well

Before I start the meeting, my mic works. And when I start the meeting, my microphone works but not well. After waiting other people coming into zoom meeting, I start to speak, but my mic is dead (I surely unmute my mic, and choose the right mic), I have to struggle for 1 or 2 mins by speaking repeat and after other people hear my voice, I have to start the real conversation.
But during the meeting, if someone ask me a question, I reply her immediately, but they couldn't hear my voice at the beginning (like very low voice)
I use zoom for 3 years, I haven't faced this kind of issue.
I uninstall the zoom app and download a new version. But it is still not working.
(I have tried the troubleshoot guideline)