I"m sorry to hear of this with Ernie. Disorientation and confusion are signs of a change in mentation (mental status) associated with encephalopathies (brain disorders). Panting is also consistent with central nervous system disorders although can represent both medical and behavioral problems. It's often seen with elevated ambient temperature, exercise, anxiety, or perceived pain. To confound the diagnosis further, it's also seen with fever, narcotic administration, glucocorticosteroid (prednisone, e.g.) therapy, Cushing's disease, hyperthyroidism, hypocalcemia, pheocromocytoma (an adrenal gland tumor), cardiac disease, tachyarrhythmias (fast irregular heart rates), brain disease (as mentioned above) and obesity.
Ernie may have been awoken by a complex partial seizure (previously called petit mal and also called psychomotor seizure) which is described as abnormal focal or asymmetric sensory or motor activity affecting any part of the body and which may be associated with autonomic signs, (salivation, vomiting, e.g.) and is associated with a change in mentation (mental status) and/or behavioral abnormalities. Sleep is the most common post-ictal (post-seizure) symptom. Mark your calendar for this event and for just what you witnessed. Ernie's vet will need all the information you can gather when deciding if Ernieshould be prescribed an anticonvulsive drug. Most of us will accept one mild (lasting less than 5 minutes, no thrashing about, no loss of consciousness) event monthly before prescribing such a drug. Should he suffer another event within 24 hours of this one clustering is diagnosed and that may presage status epilepticus - the state in which seizure activity doesn't abate unless I heavily sedate or anesthetize my patient. He would then need the attention of a vet at your earliest convenience.
Seizures first arising between the ages of 1-5 years are usually considered idiopathic (unknown cause) epilepsy. Seizures arising after 6 years of age are often caused by brain tumor or, less commonly, adult onset epilepsy. Please respond with further questions or concerns if you wish.