Judder after new cam belt

I've just recently had my cam belt done and ever since, after the car has been running for a little while there is a judder that is on/off as it is stood idling.

It looks as it is been caused from the back of the engine, as it is shaking the whole of the exhaust. But when you engage the clutch or pull the gear stick back towards forth it stops the judder.

Just wounded if anybody else have experienced this or know anything about it, as from reading post on here leads to it been a mount or timing been a little out. Also the soda dealer said it is possibly the flywheel on its way out.