The world number three, who received a bye into the second round, looked to be cruising after sweeping through the first set but her Polish compatriot Linette soon turned the tables to cause the event's first major upset.
"Tennis feels complicated in my head," Swiatek told reporters. "I know it's supposed to be simple. In terms of my mentality and how I feel on court, it's going to take a while."
The 24-year-old said her tactical game unravelled in the second and third sets, contributing to her first opening defeat since the 2021 WTA Finals.
"It just was a bad match for me ... unconsciously, or consciously, it's hard for me to say. I need to work to get back from that, because I haven't felt things like that for like five years," she added.
"I'll just get back to work, try to get something positive out of the practices and try to figure it out."
Linette, 34, played down the significance of the win.
"I don't like to make a fuss about it because there aren't too many Polish players, so there's a little more attention," said Linette, who plays Alexandra Eala next.
"Obviously Iga sets such a high standard for us that's often not reachable.
"I think it was an amazing win for me, it means so much at this stage of my career but I don't want to comment about it in a way that could put her down."