Samething is happening to my G35 and i keep thinking it may be the battery. My brother had the same problem with his G but now it is fixed. he doesnt recall getting a new battery, but i think that should solve the problem.

 

I have a 2003 sedan and my alarm would go off normally when temperatures were warming up. Would happen anywhere. Learned that it was the hood pin switch for the alarm. i simply unplugged it. The pin switch on my car was on the passenger side. it's black. I haven't had my alarm accidentally go off for months now.