Front end problems

I have a problem with my 73 duster. I really hope someone can help me. I've only owned the car about two weeks when I drive the car about 5-10 minutes it feels like the front brakes come on buy them selves and it will start bouncing like I have a flat tire. The brakes don't completely lock up but there on, if I let off the gas it's enough to stop the car right away. The front brakes are disc and the pads look new. I'm stuck everything looks good but I can't figure it out. Has anyone else run into something like this or have an suggestions on what to do I would appreciate it. Thank you in advance