Anakin and Padmé were both fast asleep – because that’s what people normally did at night. And he was not so connected to Siri that her popping out of detection caused him to snap awake. He was ready to sleep through the night if nothing as demanding as a droid army invasion showed up.
But Obi-Wan’s very loud and forceful projection jolted Anakin like an electrical current. He almost jumped out of bed before he was fully awake.
Heart pounding, he reached for his lightsaber on his bedside stand and held up his hand cautiously to Padmé, “It’s Obi-Wan.” Though, that could mean any number of dangerous things were about to descend upon them. He didn’t pause to throw on a shirt, he tread on bare feet in his pajama pants alone; when it came to a battle, a layer of cotton wasn’t going to give him all that much more protection. As he approached the door he reached out with the Force, for a warning, so he wasn’t walking blind into a trap…
And felt nothing out of the ordinary.
By the time he opened the door, he was more confused than concerned. “Obi-Wan? Why are you waking me up? What’s going on?”