Is my starter motor knackered? On my 3.9 v8i petrol

Hi everyone hope your all safe and well and having a good Christmas break with your loved ones?
My question might be a simple one to answer but I need a second opinion.
I've recently replaced my cylinder heads and gaskets after over heated problem with coolant spewing out of expansion tank . I've replaced a ton of stuff, inlet manifold ,waterpump coil, , fitted dual battery system with red optima batteries so loads of power. When I crank to start some times it sounds like the starter is labouring and others it spins sweet. So is it for the scrap heap or can I service it or just get a new one?
Any advice would be appreciated
Keep safe and well guys and gals and hope to meet up maybe on the green lanes
Dave

Starter motors can be refurbished so not a big problem - take it off, leave with auto electrician, pick it up when done and refit.

However, I have seen starter type issues and the first try has to be disconnect the battery, then remove the big wire from the starter motor, clean the terminals and the end of the big cable then reassemble. Next, remove the little wire from the starter motor, check the wire hasn't gone hard and brittle - if it has, cut the spade connector off and replace with a new one but make sure you don't cut too much wire off or you'll have to put a connector block in to extend the cable so you can reconnect it. Again clean the terminal and reconnect. Make sure you note which wire goes where, some starters have an extra terminal. Then reconnect battery and give it a spin.

While you're playing with wires, maybe remove and clean the main earth cable connection too.HTH

Thanks kev, it seems I'm finding niggle after niggling fault trying to start her. I put this out there as I didn't want to bother or disturb you after all the help this past few days. But a real big thanks.
So if I clean it up check wiring and earth hopefully be OK?
Just another job added to the list lol.
I'm not giving up I've done to much to just pack up.
Keep safe and well and have a happy new year. We could all do with a good year to come after this site shower of a 2019
Dave

One piece of advice, if I may...

With your cellphone, take a picture of the starter motor and wiring before you undo all the wires, it'll help as you want to reconnect them and can't remember which goes where...