Wobbling and burning smell problem Options

[smiffythecelica]

After 20 minutes driving on country roads at 60mph I've gone into a town area to drive at 30mph and after 2 or 3 minutes the car has started wobbling/vibrating up and down on perfectly flat roads. The wobble even occurs when I have the clutch pedal full down (i.e. gear not engaged at all). This is accompanied by a burning smell which is coming from the front of the car (don't know where exactly).

This has happened 3 times over the last 6 weeks. After the car's been allowed to sit still for a few minutes the car drives fine again. I don't have a worn out clutch as I've tried accelerating hard in 5th gear and the revs don't jump.

I've had Mr. T take it for a test drive and have a look over it and no problems were found. Any ideas? Don't know if it's related, but there is a rattling sound under the bonnet that I get when the engine is cold.
Cheers,
Dave.