1995 Mercury Sable - Intermittent Starting Problems

I have a '95 merc sable. about a month ago i started having trouble getting it to turn over. the starter cranks hard, but the engine would not turn over. this would only happen once every few days. sometimes i would crank it a few times and it would start, other times i would have to wait 10-15-30 minutes and go try it again and it would fire right away. I have a new battery within the last year, new starter within the year, and just replaced the fuel filter, i am about to replace the fuel pump. Over the last month or so the issue has been happening more frequently, almost daily now.

Recently, (withing the last few days) i will be driving down the interstate and my car will suddenly stall. i pull over to the side of the road and try to start it, again it cranks hard but does not fire. if i sit and wait 10-15 minutes it i can get it to start on the first crank. There seems to be no coloration between time of day, air temp, engine temp, humidity, etc. As far as i can tell there is no common denominator with the issue.

This leads me to believe that it is something electrical but all the reading i have done doesn't seem to point me in a for sure direction to what the problem is.

I NEED SOMEONES HELPCar Repair Talk's forum.