2002 Ford Focus

I have noticed a heavy vibration in the front end of my car when I reach speeds of around 60 mph and it worsens greatly around 70 mph.

Yesterday, I was driving at 70 mph on the highway and my car suddenly decelerated to 40 mph and would not accelerate no matter how hard I pressed the accelerator. I stopped the vehicle and turned it off. After restarting, it did the same thing two more times, the final time while I was going only 55 miles.

After the car sat for a an hour, I drove it back home and didn't have any problems at all. However, I drove it home a different way and never went over 55 mph.

Any suggestions?