Slam and squeal?

Thanks in advance for any advice or help... I have a 2010 outback which I purchased in 2015. In the last year and a half the car has started hesitating and squealing. It happens between 45 and 70 mph, and sporadically. When I’m accelerating (usually on a highway) I can feel the car begin to lag for a few seconds, followed by an abrupt jerk or lurch then it makes a loud squealing noise, like a belt has just caught after not slipping correctly. I always notice that the lag happens at around the 2nd rpm and then when it slams or jerks it jumps up past 3, but then calms down and drives normally after the squeal. The dealer can’t recreate it and it will only happen periodically. Once it starts doing this though, it will do it for the next day or two, but may go for a week or two between episodes. Anyone have a similar issue?