92 q45 start then no start.. drains battery.theft alarm wont work.

[ladyq45]

my 92q45 will start when it wants to I had alternator checked and it was good the battery is new and that didn't help. When I drive it is fine and then for some reason it wont start up I can drive to the store and then go home then when I get in to go again it wont start and the battery is dead. once to bring it home I had to be jumped three times because it would go dead while driving it .. ..also I notice the car alarm doesn't go off anymore it is an infiniti alarm system it use to work..any suggestions would be appreciated..Thanks

[maxnix]

Try taking it to an automotive electrical shop. Let them retest the battery and alternator, then if they pass, have them observe the car for excessive current draw. If there is one, they will have to trace it to its source.