Indexing Stuck in Zero!

Why does indexing get stuck on 0 (zero) percent? After a while it goes away.  It's like it did index the new downloads but most of the time it shows progress like 26%, 50%, 96%, etc. until it reaches 100%.

Lately, it's been getting stuck on Zero percent 0% 

Thanks!

DAL

Ps. I know there are similar threads, but couldn't find them for some reason.  Maybe the problem has not been resolved.