I got this same problem few years back,where the engine turn off by itself when i stopping e.g at trafic light or when trapped in traffic jam,sometime it can start immedietaly,sometime after cranking few times it can start,sometimes after cranking many many times it wont start at all.
same also like i drive then i stop at grocery shop,it wont start and after waiting for some times like 10 to 15min,it will start again,i have bring them to lot of workshop,hundred of answer i received,ranging from o2 sensor ro fuel filter,to fuel pump and wiring problem. At times i almost give up with the car cause it cause me trouble and embaresment with this problem.
i have change the o2 sensor,fuel pump and filter and do lot of diagnostic problem which cost me thousand,but the problem still coming back,even i admit it ok for a few months but then at some time it coming back. I completely clueless,feel like i want to throw the car into the river,but luckily not cause i love altezza, well back to the point,after sometime i meet a mechanic and he check the whole car,then he found out there is one long wire frpm engine connected to the crankshaft sensor, and the wire inside became brittle because it located beside of engine, and he say the electrical signal maybe not clear like astro service when it is raining,so he replace the whole wire,which cost only around $2,and until up to date,the problem never happen again.
