fast start

i have a 1995 jaguar XJ12 and recently i just changed the spark plugs. I knoticed that when i start it now, it starts way too fast...like a split sec. if i turn the key a little bit longer, i could hear the starter motor grind with the flywheel. basically, i have to turn the key and release it right away for it to start normal, but doing that is kind of tough. i have been grinding the starter and flywheel twice or three time a day now on average..anyone know how to fix this problem?

first on the v12 the sparkplugs are hard to change
i would check if the sparkplugs where screwd straigt in and tight
because you can crosstread the plugs real easy on the aluminium heads
check if they dont leak when the car runs (compression loss )
than it turns realy fast when you start
thats what i would check first

i took my jag to the mechanic to change the spark plug..some people told me its just the starter being loose and not retracting fast thus the teeth of the starter motor grinding on the flywheel or torque converter...should i just change the starter?

The way the starter gear works is by being pushed outward by the rotating motion of the starter..if the flywheel is moving fster than the starter then the gear will be pushed back in or freewheel, unless the starter is still powered...I would check the starting injector. if is leaking it will flood the intake with fuel, causing the car to fire off quickly. like pouring gas into a carburettor.