Berlin has Christmas Markets in various tastes, some on weekends only (reco for Dec 6-8 is Alt-Rixdorf). While the ones on Alexanderplatz are very partyish / entertaining, others are focussing more on Christmas related topics. You can see that they are spread over the city. Btw: the Gendarmenmarkt one is moved to Bebelplatz this year.
Hotel recommendations depend very much on price level and kind of hotel style. Staying along the central train axis between Alexanderplatz and Zoologischer Garten is meaningful.
Staying around Zoo you will have a beloved Christmas Market infront of your doors and / or windows. Also the buses to Charottenburg Palace with Christmas Market (?) start from there.
If you like the partyish ones stay at Alexanderplatz.