Reliant Fox noise

Really needs a tech to listen to it but check the crankshaft pulley for twist.
These days they're called harmonic ballancers and can fail producing some odd noises.

t Answer: The problem is the camshaft dephaser pulley. This pulley is part of the variable valve timing system on your engine. Once the engine revs get above a certain threshold, a solenoid valve opens and allows oil to flow to the dephaser pulley. the oil pressure works against vanes inside the pulley and rotates the outer part of the pulley, this in turn alters the engines valve timing giving the engine more power at higher revs. The problem is that once the engine revs drop down, a locking device should engage inside the pulley. The locking device fails and allows the pulley to move when you start the engine, hence the rattling noise. Because of the excessive amount of movement generated during start up the locking device engages, so when you restart the engine the noise is no longer evident. This is a common problem on the meganes and renault spent approx 4.5 million pounds on a solution to this problem ! A modified pulley was produced, and the engine management ecu needs reprogramming when the new pulley is fitted.