If it’s not too personal, do you mind if I ask what kinds of “subtle hints” your wife is employing that you miss until later? (I think it’s better that you notice, eventually, than if you never noticed at all! :))
One suggestion is to initiate straight-up foreplay without actually initating sex. In other words, come up to her when she’s busy with something, give her a kiss on the back of the neck, etc. and then … let it go. Walk away. Gets her thinking about having sex with you.
Then, pay attention when she goes from thinking about it to initiating it with you! 