Sometimes he gets hot with his girlfriend. Other times he gets cold with her to get her to come to like him more.
Is this the right expression?
For example, at first he spent much time dating her. Later he spent less time dating her. Actually, he loves her a lot. He wants her to love him more. On purpose, he pretends he is losing interest in her. He thinks such tantalizing strategy has a good effect on the romantic relationship. As a result, she can't help doing nice things to him more than before in order to recover their relationship.