"I first sensed" is correct and usable in written English.
This phrase is used to indicate that you perceived something before any other time. For example, "I first sensed a strange smell coming from the kitchen."
Fifty years ago, as a child, I first sensed the shattering beauty of the Parthenon.
I first sensed this attraction travelling there with my family as a 14-year-old.
There was this birthday, I think my sixth, when I first sensed... " — and his chin would nestle closer and closer to his chest, his head would drop farther, so that I was looking right at his bald spot.
It is when I first sensed that the fight in him was probably finally over.
I actually first sensed that we weren't getting the doomsday we were promised on the morning of the referendum result.
And he was 28 when he made 'Jaws,' the same age I was when I made 'Sixth Sense.' Maybe life has orchestrated itself that way, or if it's destiny or what.
"That's where I got my first sense of community service, of looking outside my immediate world," she said.
I had that first sense of his range with the Grand Street story and "By Night in Chile".
For many of us, I suspect, our first sense of the past begins with the simple childhood request for a story about our families and ourselves.
Here I got my first sense of what those sixteenth century sailors must have witnessed when setting foot on Mauritian soil for the first time: I was on land that was 100% authentic Mauritian forest.
We went on patrol, into the casbah, and I think that was the first time I sensed the existential fear of living under constant threat.
