Amp/sub problems

Hi all, I'm having some weird problems with my amp/subs in my truck. They worked fine for a year but now when I turn my cd player on, my subs rumble and make racket without me even playing a song on the cd player. As I'm driving, if I hit a bump, the subs will respond with a loud thump. The harder I hit a bump, the louder the thump. If I've been driving for a half an hour or more, this weird thing will stop and everything will be fine. Also, if it's really cold in the morning, the subs will rumble louder when I turn my cd player on. If I turn the cd player off, the subs don't rumble. If I play a song, the subs hit when they're supposed to, but you can still hear the random rumbling. Any suggestions?
Thanks in advance

It could be lots of different things. The only obvious thing that it sounds like to me is that either your headunit or amp takes awhile to heat up, and within that time something is reacting to it. The bumps, I would think would be caused by something loose in your amp or headunit, or even your RCA inputs on the amp. Check to see if everything is tight, and next time you hit bumps, see if your headunit jumps around. But if you turn off the headunit and the subs dont rumble, the only possible thing for it to be is somewhere between the headunit and the amp, or in them somewhere. It cant be your subs, so dont worry about that.