I find it very embarrassing, but during conversation I can't help yawning. I'm not over tired and it happens during the day and in the evening. It can be when I'm in the middle of speaking and so it gets embarrassing especially if in a meeting!
How can I stop?
Yawning can be caused by nervousness and not breathing properly. If you are speaking at a meeting and not too confident, this could be the cause. It can happen because of hyperventilation. I know how embarrassing it can be because it looks as if you are bored. Try to take some long deep breaths before speaking at a meeting. It can also happen if you are a very quick speaker and don't take enough breaths.