1999 Ford Mustang why is my car shaking as soon as I crank

Shakes or Wobbles problem
1999 Ford Mustang 6 cyl Two Wheel Drive Automatic 158, xx miles

I just bought it. It has a slow start to it, and sounds like its going to die when starting, but generally takes about 10 seconds to sound like its running alright. But it really shakes even when just turning it on, and especially really bad after 35 mph. They guy said it was cv axels that sold it to me, but I am starting to wonder if it might be engine mounts, or the cat converter? Any ideas? I think it has an exhaust leak too.