What causes a 3800 engine to shake real bad in a 1996 Chevy Camaro?

Try checking your engine mounts and bolts. On my Engine was it a misfire condition,the sparkplugwire from cyl #6 came loose I have a 96 Camaro RS 3.8 L.The other time it was a small Vac Line by the Throttle body,that caused a bad shake