Hi Mommasride,
There are two mechanical interlocks in the SLA - a cable from the ignition switch and one operated by a solenoid deep in the guts of the SLA - you only get to the solenoid after removing most of the SLA parts. There are also spring-loaded paws that might bind if debris gets in them. I think the cable interlock only prevents you from moving out of park (but I might be wrong). Your issue sounds more like the solenoid is starting to have some problems. If you do decide to remove the SLA, before you go all the way, after you have removed/moved aside the upper console, disconnect the mechanical linkage from the ignition (it's on the front slide of the SLA (towards the engine), biased towards the passenger side, takes half a turn to disconnect) and see if the issue persists. If the issue goes away, it's probably an adjustment like 180 said. If not, maybe it's the solenoid.
-Jerry