My car will randomly not start

Do you mean that after you removed the wrong key your original key wont go in, or do you mean using your original key and turning the starter it wont start or even turn the ignition on. If you tried to turn the ignition switch with the wrong key, sometime it will cause the lock to turn freely as an anti theft measure. You should be able to find the way to fix this in the user manual that comes with the car.

TRY REPROGRAM KEY .PUT KEY IN IGNITION SWITCH TURN IGNITION SWITCH ON POSITION 20 SECONDS DONT START ENGINE WAIT 20 SECONDS TURN OFF SWITCH THEN TURN SWITCH BACK ON 20 SECONDS WATCH THE THEFT SECURITY LIGHT BLINKING.WHEN THEFT STOP BLINKING VECHICLE WILL CRANK.IF LIGHT STILL BLINKING.TRY FEW MORE TIMES KEY IN SWITCH ON POSITION FOR 20 SECONDS.MAKE SURE YOU HAVE THE CORRECT CAR KEYS IN SWITCH IF NOT WRONG SET OF CAR KEYS WILL SET OFF THEFT SECURITY SYSTEM.IF KEY RESETTING TRICK DONT WORK.CHECK BATTERY POWER MAKE SURE YOUR BATTERY HAS 12.5 VOLTS AND CHECK SECURITY THEFT FUSE.IF ALL LOOKS GOOD YOUR SECURITY HAS TO BE CHECKED OUT AT THE DEALERSHIP.

My cobalt turns over but doesnt start up and i dont know whats wrong with it to get it fixed.

If you had battery unhooked and assuming that it is turning over try this Put your key in turn it on dont start wait 10 mins remove key wait 10 seconds repeat this a total of 3 times. If that dont work try a different key do the same thing. This relearns your key to the ignition it started with Gm cars and trucks from 1999 to to 2006. It is a big problem but there is no recall that I know of. If that dont work a dealer needs to probably replace and reprogram your ignition switch and keys

Is your theft light flashing. If it is try this. I learned this from emission wiz Put your key in turn it on dont start wait 10 mins remove key wait 10 seconds repeat this a total of 3 times. If that dont work try a different key do the same thing. This relearns your key to the ignition it started with Gm cars and trucks from 1999 to to 2006. It is a big problem but there is no recall that I know of. If that dont work a dealer needs to probably replace and reprogram your ignition switch and keys

will tace abaut 10 min to fix problem,sit on dreiver seat and turn key on only dont cranc ower weit 10 min or litlbrt more ,securiti leigth will strt flushing imidietly turn key off and start engine if dont work repit prosigure dhis will reset antyteft sistem in car

It's the ignition switch.You will have to replace it.

98 buick lesabre wont crank with key. When I cross the starter it runs great for 10 seconds and dies.

the steering wheel SHOULD be locked if the key is not in the ignition and turned to the 1st position.  If you can turn the steering wheel more than an inch or so without the key n the first position,  the ignition switch (read: thingy you put the key in) is bad.   
Sometimes you may have to move the steering wheel slightly to one side or the other to get the key to turn,  this in itself is not a cause for alarm. Try it and let us know.  If this doesn't work, you are probably looking at a couple hundred dollars parts and labor to get the switch/steering wheel lock mechanism fixed.
Please rate all solutions.

put the key in the ignition for 10 seconds then turn the car over and then turn it off see what happenes if no luck contact me ill find out how to reprogramme it for you