Why does my dog do this?

[midlifeattheoasis]

Every evening when we’re sitting on the sofa, my 13 year old Jack Russell has started jumping up suddenly from his sleep. It’s always around 8/9 o'clock and it’s as if something has startled him. He then goes back to sleep on the floor.

A quick google tells me it could be any number of things, but I wondered if anyone else’s dog has done this?

Many thanks

Animals outside? My dog is often jumpy in the evenings because he can hear/smell foxes outside. Night time is an exciting time for dogs!