My radio works intermitently

My radio works intermitently. Sometimes when I'm driving it will come on, then it will go off on its own. There doesn't seem to be a rhyme or reason for it.
A couple of years ago it would do this and only stay off for a few minutes then come back on for days. Now, I never know when it will come on. When it does come on now, sometimes it goes off and I hit the increase volume botton on the steering wheel and it will resume. It doesn't matter if I am playing the CD, radio, of cassette.