Renault Scenic problems starting

Engine turns over and attempts to fire, it fires up but in the background there is a rattle like something touching an alloy casing. Sometimes it stalls. On restart it repeats, then usually on the third attempt it starts quietly. This noise is not always apparent on start up, sometimes it starts as you would expect, sometimes it starts quietly then stalls. This happens mainly when starting from cold, but also happens when engine is hot or warm. Sometimes it misfires for a few seconds while starting then runs fine. When running it runs fine, (have replaced several coils but not for this continuous problem). Any electrical items which could, or, will cause this annoying starting problem.