I don’t login here often too, but eventually I’ve found reason - negative battery terminal design. My issue was - it seemed tight, but under vibration - it would slip breaking connection momentarily which led to power disconnecting and causing car to look electrically dead. When car stopped starting - it appears to me it was just dirty on the inside, so proper cleaning resolved the issue. P.S. as for waterpump - my timing chain started to rattle a bit on cold starts so I changed it last week alongside with oil pump chain and water pump as precautionary measure. My car clocked 240k km or around 149k miles. P.P.S. Previous owner assured me that timing chain was already serviced after I took the car.