It's different for different people
For me just before a breakdown I am unable to make decisions even small ones as every daily decision is usually left to me.
Snapping at people for tiny things.
I get a twitch in my right hand that gets more pronounced the more stressed and anxious.
I stop taking care of myself and the home, have no energy.
Then it's like I'm disconnected from myself watching from behind a window I can see what I'm doing but can't change it
Other people will react in other ways some are common reactions some less so
Are you worried about someone or asking for yourself?