1999 Pontiac Grand Am Starting / Misfiring Problems

I got this car in 2004 with 32000 miles on it. After about 6 months to a year I started having issues with the car starting. It did not depend on time of day, season, weather, or if the car had recently been driven or not. The car would every once in a while just not start. It will crank but not start. If left alone for 15 to 30 minutes it will start with no problem and without having been adjusted in any way. It will happen periodically throughout the year and has been doing that the entire time I have owned the car. No one seems to be able to diagnose the problem no matter how many times I have had it looked at. It also started having misfiring issues last year. I replaced the boots, spark plugs, and coil housing. The misfiring stopped for about 8 months and has recently started again. It it most likely to occur when accelerating and shudders when idling. I replaced the spark plugs again last week and it seemed to lessen the jolt when it misfires but did not stop it all together. I am not sure if these problems are related in any way, but it would be great to get both of them resolved.