My experience dates back to 2009, so things may be different now.  Back then, there was a desk for transit hotels right after entering the terminal where you would pick up the hotel voucher (issued by a Nepali gentleman in my case).  You would then proceed to the immigration desk (mostly staffed by burka-clad ladies sporting expensive-looking watches and mobile phones).  Entry was granted without any question asked.  Clear customs (be sure not to carry any alcohol or pork product), walk outside the terminal to wait for your hotel's van.  Experience the desert heat for a few minutes before you enter the vehicle with AC in full blast.  You need to surrender your passport at the reception desk which will be returned at check-out.  Dinner and breakfast were on the house.  There is a good chance that your chaffeur and hotel staff are fellow Nepalis (chaffeur from Palpa and hotel staff from Chitwan in my case).  All in all, it was a pleasant and hassle-free experience.

You may also want to check with the Qatari consulate/embassy and/or visit their immigration website.  The airport's website may also provide some helpful information.

Enjoy your trip!