Engine hesitates then has spikes in RPMs

When I’m driving the car will hesitate around the 2,000 RPM mark to then suddenly have a spike to around 4,000-5,000 RPMs and jerk somewhat aggressively sometimes, and also when I step on the gas it feels like there’s a small delay for the car to react compared to other cars I’ve driven (might be in my head). There’s also been occasions (like 2 or 3 times) when I’m driving and I step on the gas to have no reaction at all for like 3 seconds and then the car will accelerate. The hesitation will happen more often when going uphill and the car will start to jerk. I’ve gone to 3 mechanics and they tell me to wait for the check engine light to appear for them to be able to do something to it since currently it doesn’t have it turned on but it’s had this problem for maybe close to a year without the check engine light going on. I’ve been told I should go to a transmission mechanical shop to get the transmission reconstructed to see if that helps but it’s expensive and it might set me back which I don’t mind if it’s for sure that it’ll fix it but I want to know if maybe there’s something else that might be the issue before doing that.