Yes, I have woken with a bitten tongue a few times or so.

Each time was due to my partial seizure becoming secondarily-generalized (tonic-clonic). It's certainly worth mentioning these biting events to your doctor. They'll probably want to do an EEG to check out the electrical activity occurring in your brain. I greatly recommend the EEG (preferably one with sleep or extended time).

Very best wishes to you!