I believe your car has wiring problem. Same goes to me last year. At 1st the mech thougt it was the alternator, but after changing, the same symptoms happened. Then he checked the whole car wiring, got one wire got shot with the body/ engine. He fixed the wiring, and the problems gone. But, my v6 was in the workshop for nearly a week for the mech to trouble shoot the problem. Make sure your mech is a very "penyabar" person... All the best bro!
already checked.. but not at car wiring specialist. just ordinary workshop but not 'bawah pokok' one. but normally every workshops have their expert person for each type of job (air cond, wiring, engine, radiator, gearbox, electrical parts ect). when the wireman checked... he used one equipment (i do not know the name) and found everything running in good conition. he on/off air cond, on/off head lamp, sport light, every electrical parts... the 'equipment' indicator shows normal... not very big varians...
thar day also sent to wiring specialist in sunway with mr.rakesh but still cannot find the problem. but... maybe... as you said... must leave my car and let the 'penyabar' mech search the problem..
or maybe.. like danz said.. must check my remote control key coz mine one also start 'gila-gila' already... sometimes malfunction.. have to 'tok..tok..tok..' (knock) a bit then press...
see laa... any progress will update later..