忽冷忽热 [- lěnɡ hū rè]sometimes hot and sometimes cold; blow hot and cold in turn; by fits and starts; Fever alternates with chills.; now hot， now cold — sudden changes of temperature; sudden changes in one's affection [attitude; enthusiasm]：
•¶ 在工作上他总是忽冷忽热有冬有夏。 His enthusiasm for his work blew hot and cold.