vt really weird starting problem half firing keep running with key out?

Hey i have a 99 vt ex that usually has been running fine.
but recentily its started to have some starting problems by which i meen when i turn the key it takes longer then normal to crack or it has a really ruff start like i didn't hold the key for long enough.
What really got me scared is today i went to supercheap, i went in a brought a few things then when i went to leave i tryed starting the car but it failed well sort of. it started but only felt like half the pistions where firing and was making the nosie from when you try to start the car with the key but its already on that grinding kind of nosie.
so i panicked and turn the car off and took out the key but here the weird thing it keep running with the key out it was still going?
so i poped the bonnet and it looked like only half the pistons where firing the engine was rocking side to side like mad so i disconected the battery and it stoped.
so i was like wtf? so i tryed starting it again and heres the thing it started fine?

im not sure what is making it do this?

i could really use any suggestions because i use this car for work down in torquay and i live in ballarat so its about 250ks a day and i really don't want this to die on the highway.

the car has done 167000 km
its a 3.8 ecotec on petrol

any help would be muchly appreciated.

 

hey man i checked the error codes and it came up with 12
which i believe meens its operating normally
Another thing which might of caused it is i only just put my subs and amp back in the boot. so it might of drained to much power.
Another thing is my key is dying and somone times wont unlock the car with the button its really temperamental.
it had new spark plug and leads put on it 7000km ago along with a brand new radator and and hoses and a new thermostat.

 

Yea what would make sense and fits everything its been doing.

 

ive decided im going to take it to a lock smith tomorow and hopefully they will beable to tell if its the electronic switch or ignition barrel bacuse im not sure which is causing this problem.
thanks for all the help.

 

That is another possibility is there anyway to check to see if that is causing it?
im not really sure if i should drive it to work tomorow incase something does die

 

hey ive got a new start motor to put in to see if that helps.
but other wise i might replace the ignition.
by what i meen that it was running was when i poped the bonnet after the key was out of the ignition. the engine and starter motor where still going but the engine was only half running like the belt on it was moving about 3 inchs then stoping then moving again it was also making a hell of alot of noise . so i had to disconect the battery to stop it.