wasn't expecting this tonight

dated this guy casually for weeks, nothing serious, went home separately after dinner and drinks. but tonight, he drops me off, kisses me goodnight on the cheek, then suddenly slides his hand down my pants to feel me through my underwear. i was so shocked, didn't expect anything like that in his car, felt cold metal of my seatbelt buckle digging into my side as he kept going. it's confusing how we can be such strangers sexually even after all this time.