忽冷忽热的这个词语用英文来怎么来翻译

忽冷忽热的这个词语用英文有以下几种翻译 ：
sometimes cold and sometimes hot
sometimes cool and sometimes warm
cold and hot by turns
alternately cold and hot
如果表示对一个人的态度忽冷忽热，则可以说成
alternately cruel（ly）and kind（ly ）
sometimes cold(ly) and sometimes warm(ly)
如果表示对某件事忽冷忽热则可以说成：
by fits and starts

例句如下：
Keep sb in a state of uncertain expectation, treating him alternately cruelly and kindly
对某人时好时坏、忽冷忽热
When Mary had a fever, she felt cold and hot by turns.
玛丽发烧时，她感到忽冷忽热。
As you may know that most people in China learn English by fits and starts.
正如你所知道的，中国大多数人学习英语都是忽冷忽热