Links to the 1991 service manual are in the NSX Prime Library (red banner at top of web page). The electrical section of the service manual covers the alarm system and should provide you with everything you need ot know to fix the problem or disconnect the system.
By any chance do you have a duplicate aftermarket security system installed? If so, I would look there first. Based upon the anecdotal evidence from posts on Prime, the failure rate on aftermarket systems is >>> higher than the OEM system.
I will second the above. I had to remove my Viper alarm system. It drove me crazy. I rebuilt my starter twice, replaced and or refurbished the ignition switch too many times to count only to find the problem was with the Viper. Once removed, not a single hiccup in starting the car. Jerry
Thanks for the input. Factory alarm and realize not a good idea to post how to unplug on here. Car re-set after 2 days of sitting. Going to unplug system now that I know how to do it. Nothing but a nuisance. Thanks Marsh
The problem may actually be with the door latch switches which send a signal to the security control unit that the car has been unlocked. On a 1991, it would not be unusual for the electrical contacts to be getting dirty and starting to operate erratically. That might be something you want to check out because depending on what is happening the electric door locks may also become non functional at some point. It will also screw up the keyless entry if you have that system fitted.
If the latch switches fail you will not be able to replace the OEM security system with an aftermarket system.
Could be the switch in the door lock. I have to unlock mine from the passenger side so it don’t set the alarm off with the key. Mine went bad a while ago I just never pulled the doors apart to fix it yet. Have you tried unlocking it from the passenger side?
Installing a keyless entry will eliminate the issue of its the door switch a lot easier then pulling the door apart. There’s a member that makes aftermarket plug and play units.