Sounds like VATS like Bonnememn said.
since you said you have only one key, you can try cleaning the contacts on the key with a pencil eraser, and you can dip in alcohol and insert quickly into the lock cylinder to get alcohol onto the two metal spring contacts that touch the two sides of the key.
Insert the key then and turn to on and wait. See if the VATS ever reads the key correctly and goes off after about 5 seconds.
I've had some troubles with VATS on my 98 and reading the key. I had gotten in the habit of inserting key and before it'* in completely I was rotating to On and Start. Sometimes the VATS was missing the reading and locking up on the first try. Wait 3 minutes and key is read and everything works.
The VATS should require three tries turning to crank with wrong key (won't work any of the tries) before it locks out the key and stays on for three minutes. Are you getting the 3 tries or is it locking out on the first try for 3 minutes.
I also considered the ignition switch contacts as the source of my problem, which comes and goes; I'm on the third time now. I considered putting in a new ignition switch-car has 140K miles with lots of start cycles on the switch in its lifetime.
Dual auto air on both