Odd sound / hesitation at startup

[Dansan]

Rebuilt my starter on 95 LC 1 year ago and no problems in 3000 miles. Recently, after attempting to start, truck hesitated and made "beating" noise, before engine caught. This occurred again after driving, shutting the truck down for a few minutes then re-starting.

It doesn't act like the usual failing starter where it will not engage at all, then will engage on a subsequent turn of the key. It almost seems like the engine wants to stall right after it appears to be cranking.

Thanks in advance for any help and apologies if this is a duplicate post.