I feel breathless within 5 minutes of sleeping at night. my tongue is dry but its all fine after i take a sip of water. i get a sound sleep after that?

Medications?: Some medications may cause dry mouth, especially antidepressants. If not, it sounds like you are dehydrated. Try increasing your water intake throughout the day and also decrease caffeine intake. If no improvements after doing this for a week i would get into a physician/medical doctor to investigate further. Also quit smoking if you are a smoker, that could be the reason also.

Rule out apnea: I agree with dr. Patel's comments but would add that possible airway blockage may also be involved. If you have a partner, do they indicate any strong snoring, choking sounds, or breathing cessation? Any evidence of those symptoms would warrant a sleep study to make sure you don't have obstructive sleep apnea.