DMF IS starting to break up as Gadget said,this in turn is cloging up the starter, normaly a quick fix is clean the starter out but will only last for a short time before the problem starts again.

The only cure for this is a new Duel Mass Flywheel, which from Ford is not gonna be that cheap, whilst youre there i would do the clutch and rear crank seal as they start to weep over time.

The whole job can cost from your local garage up to £800 depending if the exhaust comes away ok.

Best of luck.