This is a really weird one for me with my 96 SR 3.5. Sometimes the car will be fine for a day or two, and sometimes this will happen 5 times in one day. Basically what will happen is that during the day (not on a cold start, but could be 5 min later), after turning off the car, I come to turn it on...but it just cranks. If I wait 10 minutes and try again...it starts. Given that it cranks, I'm guessing it is not the ignition switch. Today it happened while at the mechanic. They sprayed the intake with carb cleaner, but it didn't help. Plus they could smell the fuel. So their thought was the it is not fuel, but spark basically. The car has never stalled or turned off on me, making me believe it to not be a coil or spark plug. No codes either. I do have another issue where at idle it will feel like there is a light misfire but again no codes. (just mentioning the idle issue in case that relates to this issue) So basically, this can happen when the car is warm and has been running all day or it can happen after 5 minutes of driving (like going to get gas and turning it off). But usually if the car has been sitting a couple of hours or all night, it starts up and runs just fine (although again, after five min and turning off, it might not start)

What could it be? My mechanic thinks it could be the ECU....just a guess. He also says this behavior is seen with aftermarket alarms...but this car doesn't have one. And I don't think the factory keyless entry could disable the car. Any relays that could play a part in this?