@paulrobert , Paul, sounds like bendix may be sticking, have you had this starter issue in previous years in the cold weather. You could remove the starter and check the bendix gear for wear/damage also look at the ring gear teeth for damage/wear/cracks. If all looks good maybe clean and relube up the starter/bendix shaft with a thin film of lithium(light grease) and if possible a little on the ring gear teeth, this may help it engage a little easier. Check out the attached links starter removal and trouble shooting, cleaning and lube bendix shaft. Good luck.
I hope this helped you out, if so let me know by pressing the helpful button.
https://www.youtube.com/watch?v=RhdSq4WOaDM
https://www.youtube.com/watch?v=lwwTrR_MWyU