Hi,
the most convenient hotel is definitly the Kempinski Airport Hotel which is adjacent to Terminal 2 (the LH Terminal).
Hotel Link I can definitly recommend that hotel. LH has an offer for the day rooms...if you fly First it is free, if you fly C it is EUR 79 for the day. PLs refer to
This page on LH Website for more info
Cheers
Bochaco
Forgot something...
Other hotels are not such a brilliant idea since thay are all off-airport. Of course there are the shuttles but nothing beats being right there