My relative is a nurse and he feels that his supervisor is looking for write up excuses and trying to get him fired. He has been written up 3 times in the last month on minor incidents. Should he go ahead and give his 30 day notice or try to stick it

My relative is a nurse and he feels that his supervisor is looking for write up excuses and trying to get him fired. He has been written up 3 times in the last month on minor incidents. Should he go ahead and give his 30 day notice or try to stick it out? If he gives his notice, could they go ahead and ask him to quit when he turns in his notice before serving the notice ?