My 2000 chevy camaro check engine light was flashing the other day twice and once today it drove nice and smoovely than i went to the gym for 4hrs came back started it no prob drove for 20mins than cut it off and it didnt start back up. what could that be?

Have a look on the following link:
https://subaru.oemdtc.com/58/diagnostic-procedures-for-p0851p0852-2005-2008-subaru

The ignition key absolutely could have something to do with it. You can probably wiggle it around and get goofy things to happen.

check that fuel is getting to engine, next, are you getting spark, are your plug wires in the right order, are they all good, you must keep plug wires from touching each other, is the cap & rotor ok, coil ok, fuses ok, do you have a fuel pump relay, if so, check fuse in relay. is the fuel filter new, did any codes get stored ECM, put drygas in fuel tank. are spark plug wires fully engaged onto plugs, don't concern your self with any smoke, let's get the engine started first, CHECK EVERYTHING MENTIONED ABOVE, including fuel filter, air filter should be new also, todays fuel w/ ethanol is garbage, for older cars. is the mass air flow sensor for this car ? aftermarkets are garbage. let me know how things work out, my knowledge is not cheap, but I will help you to avoid egg on your face, KEN

I would start with checking the computer for trouble codes.
Sounds like a bad connection in the dash wiring or key switch, but the trouble code might steer you in the right direction.

None of these codes by themselves will prevent the car from starting. I would look over the O2 sensor wiring. Maybe the harness is resting on a hot pipe. You can test the components--the sensor and both solenoid valves. Maybe there is a problem at the canister. Unfortunately, the canister and vent valve are atop of the tank, but you can still hear if the vent valve is closing when you apply ground to the white lead. The p0300 is the most likely code to affect starting. Are you getting sparks? If not, suspect the ignition module under the coils. I drive a 2000 Camaro, so I'm pretty familiar with this model.

I ran into the problem and it was corrosion on the battery terminals. on the inside against the battery. also check the the terminals for good connection.
Stay warm

NORMAL, BELT SLIPPING. CHECK THE P/S FLUID. IF IT'S BRIGHT PINK OR MILKY YELLOW THERES WATER IN THE FLUID AND NEEDS TO BE DRAINED AND REFILLED.

Welcome to the world of BMW's. return the car to the seller. you got a bad one. You got an electrical short draining the battery. Bring a blank check and sign it over to the dealer. They're going to have to run through the entire electrical system to find the short. That work alone is worth more than the a used up 2001 325i.

its not your crank sensor its your starter. i just went through the same thing. i have a 1998 chevy camaro 350 lt1. if thats not it its in your stering colum

Tps sensor will be on the throtle body, the mass air flow is befor throtle body, sounds like your problem may be a clogged catalitic converter.