Jerking after shifting gears

Hello all, new to the forum and first time poster. So I just bought a 2002 Corolla S, 5 speed (186k, 2 owner). I am really happy with it and its been running great....except recently the car has been jerking/lurching/shaking after shifting into a higher gear, once to starts jerking it keeps jerking for a few seconds until it straightens out somehow. (I have decent experience driving manuals and am matching and using good technique) The problem doesnt seem to happen on flat ground or when there is a light load. I have noticed that it is more common while going up hill? I have been reading about gear synchronization and what not but am a bit confused on how that could be the cause. I am by no means a car guy but my intuition is telling me its a throttle issue? I could be way off. I understand that its difficult to diagnose after reading that^ but I am trying to find a place to start. Thank you for any help/suggestions.
Get a LUK clutch kit. What's weird, is that I only get jerking on 2nd still, even after new clutch. Before, it was all gears though. I was thinking that maybe it's my footwork but, all other gears shift smoothly.