Why does the 2001 buick lasabre custom not start all of the time?

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2001 Buick Lasabre starts most of the time.In the last few months it starts after turning the key 2 or 3 times a few times in a month.Battery & alternator & starter OK.I was told to wait 2 seconds after inserting the key for the computer to read the chip but there must be another problem since I did not have to wait in the past.Key does not always go in smoothly, but OK in door.Is it the key, ignition switch or something else? Thank you, Phil Morey phil@pmorey.com