The delay in getting Trump's nominees confirmed is all in their vetting process -- which comes down on Trump's administration, not Congress.
There was a story posted a couple of days ago indicating that there are only FIVE executive branch nominees awaiting confirmation votes in their respective Senate committees. It was a relevant news item this week because the U.S. currently does not have an ambassador to Great Britain, for example -- even though Trump announced two months ago that he had selected Robert Wood Johnson IV for that post.
Keep in mind that a person isn't officially nominated when the President announces his selection. The person first has to go through a vetting process and background check, then gets formally nominated and sent to the Senate for confirmation.
-PJ