My E60 525i, 2004 Jan production, 87K miles, battery replaced close to 2 years, or 16K miles ago. No prior issue with this car, until -

Yesterday at 11:00am after I started up the engine, it ran about 10 seconds before died. I was able to immediately restart the engine and drove with no further issue.

This morning at 10:00am, on my drive way, the engine will not start. Dashboard lights were OK, and I could hear it tried to crank, but engine just would not start running. Then used my other car to jump start, no luck. After 2 hours at noon, tried again (no second car battery attached) and the engine started with no issue.

Any thought on what could be wrong? I feel it is not the battery, that probably rules out the alternator too. As I could hear the cranking when starting, I guess the starter motor should be OK? That leaves me with a unstable distributor or coil?

Now debating whether to bring it to the mechanic given it started OK. I do have a simple coder reader, but never used it before, and unsure if reading error codes will help.

Appreciate thoughts from this forum.

 

You should start by checking the battery connections to make sure everything looks ok and none of the bolts are loose.

 

it could be a bad, sticking fuel pump.

 

When this problem occurs, try starting longer time (10s) an then immediately check heat on connection bolts of the starter (by your hand, by carefully can be very hot). Check also battery connections. Heat = bad connection.
Also you can clean all these connections as a precautionary (on the starter first).
Can be faulty starter motor if all connections are good, random occurrence of this fault suggest it.