Visually check all the mounts. One of mine broke a few years ago and shook the car like crazy.
Oil everywhere? When was the last oil change? Did you check for the filter gasket when you changed the filter? Those are the quickest checks I can think of. Otherwise, could be pretty serious.
2006 Mustang V6 Pony Package Vista Blue with a 5-speed (Michele)
Go: BBK 70mm throttle body, BBK CAI, single custom exhaust (maxflow muffler) with polished 4" tip, SCT Tuner w/ 91 RT, SR TB Spacer, Custom made cold air bucket, Spec Stage II Clutch and SF66A Flywheel
Show: White rocker stripes, Kaenen Mach 1 Style hood, painted underhood parts/covers, Muffler tip, white stripes after heat reduction ports.
Own but not insalled- Polished Shorty Headers
Future-looking for 2007-08 F150