This video shows the issue (ignore the pulsating lights, it's just my phone camera doing that) https://www.youtube.com/watch?v=RVDjcapr0Fw
Every now and then, my car refuses to start. It'll work fine if jump started and then will work for a few days normally.
I was jump started yesterday morning and did 2 medium length drives before I parked up at home. I woke up this morning and my car was having the same issue.
The alternator has been tested & the mechanics also said the battery was fine as far as they could tell.
I was thinking it was maybe an immobiliser issue?