NEED HELP: Start button/Engine won't start intermittently after long driving

[jrnozid]

Just as the title says. To make the long story short I've been having this problem the first week I bought my e87 2005(no need to discuss about the first owner selling me a lemon since its irrelevant now). First tine it happened was when I parked the car and ate dinner then went back to the car to start the engine(insert key,push brake since automatic, then push start button) everything turns on except the engine. I asked some mechanics and they told me to disconnect one pole of the battery wait 15 mins then reconnect the pole and wait another 15 minutes. I did this and the car worked everytime. So this happened three times just to find out that my alternator is already old and had it replaced with a new one. This happens at times when I drive at least 30kms

So after replacing with a new alternator. After three weeks this same problem happened to me again, TWICE. I did the disconnect reconnect thing and it worked again. So now I'm fed up why this keeps happening because I had to do the fix everytime. Alternator reading is 13V all lights on and ircon is max while my battery is a panasonic din 88. Any thoughts what might be the problem?

[2PUTT]

if it was a manual, my guess would be the clutch switch.

have you tried checking for codes? something seems to be getting reset when you disconnect the battery which solves the issue.