My dog keeps shaking and trembling this evening — the house is warm and he doesn't seem scared

Trembling together with any of these — vomiting, wobbliness, twitching or jerking, a dazed look, a racing heart, or any chance at all that he got into something (a dropped pill, a mushroom in the garden, sugar-free gum, a nicotine pouch, a cannabis product, rat bait, a compost heap) — means stop reading and take him to your vet or your nearest emergency clinic now. Toxins that cause tremors are very treatable early and much less so late.

If he is otherwise bright, eating, walking normally and the trembling comes in bouts, the usual causes are pain (back, belly, joints), fear or adrenaline, cold, or one of the tremor syndromes. Pain is the one owners miss most, because a dog who hurts often just shakes, pants and turns clingy.

Something concrete to do tonight: video an episode, write down the time it started and everything he could have reached in the previous six hours, and look for pain by watching how he lies down and gets up rather than by prodding him. If there is any chance he ate something, bring the packaging with you.

This one genuinely needs an exam. A shaking dog with a normal exam is a very different conversation from a shaking dog with a tender belly, and that distinction is made by hands, not by a description. Your vet will decide from the exam whether this is a bloods-and-imaging evening or a pain-relief-and-recheck one.