Sorry to hear you are worried about Jeff
I'm no expert on this, but have a look at his gums and make sure they are pink (not blue or grayish). Is he panting or coughing? Also check his tummy to see it it is swollen. How old is he? Do you think he may be dreaming?
I am sure someone more experienced will be along soon
..I hope Jeff will be ok, but if he does have any other symptoms it may be worth that trip to the vet.
Let us know how he is later
x