Start with a narrower question: what is different tonight? A dog who has always taken a few laps before settling is in a different situation from one who suddenly paces for hours. The hour they wake, and what they do next, narrows the list faster than a guess.
Some patterns point straight at the cause. A dog who walks to the door is asking to go out. A dog who is wide awake at bedtime probably napped through the afternoon or missed the sniffing, training and puzzle work that tires a brain. A dog who wakes at the same hour every night may be hearing the heating system or a neighbor’s car. Moving between beds and the floor usually means the room is too warm or the bedding is wrong. Panting and pacing with no obvious trigger can mean pain, which is worth a vet call rather than another night of watching.
Senior dogs rewrite the schedule
Older dogs often sleep differently. Vision and hearing changes, stiff joints and bathroom needs can push a dog out of bed, and a dog who wanders familiar rooms after lights out is not being difficult. A recent look at what senior dog blood work reveals about aging is a good starting point before the next appointment, and shorter evenings mean fall walks now happen after dark.
What this means for your dog
Track the hour and where your dog goes for a few nights before you change anything. Load the daytime with an unhurried walk that allows sniffing and a few minutes of training. Keep middle-of-the-night trips quiet and dull, because a snack at 2 a.m. quickly becomes a standing appointment. Call your vet when the waking is new, keeps repeating, or comes with changes in appetite, thirst, bathroom habits or mobility. Two signs mean going in tonight: a swollen belly with retching that brings nothing up, or trouble breathing. Restlessness is sometimes the first visible sign of bloat, and it is not a wait-and-see symptom.