blow hot and cold
blow hot and cold  {v. phr.}
To change your ways or likes often; be fickle or changeable. 
Tom blows hot and cold about coming out for the baseball team; he cannot decide.
Mary blew hot and cold about going to college; every day she changed her mind.
The boys will get tired of Ann's blowing hot and cold.
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Source: A Dictionary of American Idioms

