The sport's most successful driver of all time, with a record 103 wins and seven world championships, gave a downcast assessment after qualifying eighth for the Saudi Arabian Grand Prix in Jeddah.
The Briton will line up seventh on the grid thanks to Ferrari's Charles Leclerc, who qualified second, dropping 10 places but teammate George Russell got far more out of the car and starts third.
Once-dominant Mercedes had only the fourth fastest car in the March 5th Bahrain season-opener won by Red Bull with double world champion Max Verstappen leading Mexican teammate Sergio Perez.
"I just don't feel connected to this car and no matter what I do and no matter what I change, I can't get confidence in it. I'm at a bit of a loss with it," Hamilton told reporters in Jeddah.
He said he struggled particularly with the car feeling unstable on his set-up through the high-speed corners.
"Maybe it will be OK for tomorrow. I wouldn't hold my breath," he added.
"I just don't feel the car underneath me...I don't really know what I am going to do about that."
Mercedes team boss Toto Wolff recognised his drivers were having contrasting reactions, with Russell positive about its handling.
"They need a car with a certain behaviour in order to drive fast and Lewis, at no time this car has given him this season any feedback that allowed him to push to the limit," said the Austrian.
"If you haven't got that car underneath you...(in) sector one you are never able to push it fast through the corners. This is what we've seen. It's all sector one and George just drives around it and is able to have more confidence in the car."
