Something wholly unexpected.

As you start thinking it's time to pull back and let her enjoy her new car, Kayla suddenly runs a hand up behind your head, and pulls you into a kiss. The action is so sudden and unexpected that you drop your keys on the ground and grunt with surprise, but your lips and tongue have other ideas: you return her kiss with interest for a few seconds before breaking away...
"Kayla..." it's a breathy whisper. Her hot tongue in your mouth had been an electric shock that sent your head spinning. "What are you doing..." your hands are on the small of her back, and hers are gripping your shoulders from underneath your arms.
"I don't know..." and she locks back onto your mouth with hers hungrily. You can't help but slide your hands down over her ample ass, and you explore her hot mouth with your tongue. Her hands are between you now, rubbing your chest and gripping your pecs.
"We..." you pause for breath as she kisses your neck, and pulls up the front of your shirt to rest her fingers inside the waistband of your shorts. "...we shouldn't be doing this."
"I know." her eyes are unfocused, and her hand reaches inside your shorts to grip your growing cock. When her fingers close on it, she looks into your eyes... "it's wrong." There's a serious disconnect here between Kayla's actions and her words. "But it's been so long...I haven't had...a real...you know...since Frank..." she was squeezing and stroking your cock inside your shorts. "I've never noticed before, what a sweet guy you are. And good looking too." Her free hand grabs yours, and guides it to her chest, and she squeezes your palm over her left tit. Real or fake, they feel good, and you can't help squeezing and teasing the nipple on your own.