1999 Chevy S-10 location of security passlock

Electrical problem
1999 Chevy S-10 4 cyl Automatic 150,00 miles

I think the security passlock is the problem but don't know where it is located....Can anyone tell me please?

Thanks...

ps it will crank and turn over for about 3 seconds then quit...it may take 5 tries or 50...but once it stays cranked will run flawlessly....