Starter solenoid contacts?
It took me a year of "will it start" for me to finally change out the starter motor and then all was well.
I assumed the problem was everything else other than the starter as my starter motor checked out OK. As such, I assumed it was OK - and it was strictly speaking.
The problem was the starter solenoid contacts. The engine turnover concern was most often only at first start in the morning or in the evening if the 3 had sat all day.
Also if I kept the battery on my CTEK US3300 trickle charger overnight, engine turnover and starting was never a problem.
I eventually concluded that the starter solenoid contacts needed the extra couple of volts a full battery provided and all was well, but if the battery was a bit low, then the solenoid would not function.
LR sells the solenoid separately; Denso sells the contacts separately or you can just replace all as I did.
