I've had two 91 TT Zs and they have both done this. Only does it a couple times a week, but when it does it I have to let off the key and it normally starts right up on the next try. What I'm really wanting to know is could too much grinding from the starter cause a clutch/flywheel engagement issue? My clutch slips sometimes in first and I'm only running about 300whp. I've never had to deal with anything related to the flywheel or clutch so I don't even know how it's set up with the starter. Thanks.