Based on the fact that you listed the odometer reading in KMs . . are you in Canada?
If so, the weather is getting cool this time of year. The already undersized battery of ?? age is probably not putting out a ton of cranking amps. Even if it "passes" a battery test, it may be worth the v6 upgrade. I did mine, and it starts right up, even below 0. If you search, I posted pics and everything about a year ago.
Is it that the engine is turning slowly, or that it turns quickly but for a long time? The slow turning is a sign of a weak battery, the long time to fire up could point to plugs. If it's turning normally with no odd noises, its probably not your starter.