Running out of fuel after 7 hours is not usually associated with pilot suicide flights.
Pilot suicide flights are usually over quickly. eg GermanWings
I think there was a history of mental illness with the perpetrator of the GermanWings crash.
It's been suggested that if, as has been speculated, the Captain of MH370 had taken control of the flight and deliberately navigated it to the Southern Indian Ocean, his motivations were very different. If all you want to do is kill yourself, there are easier ways to do it. But if you want to leave behind a huge mystery and maybe cause enormous embarrassment to a government you are bitterly opposed to, then it makes sense.