Definelty try Spelger's advice.
Also, you might want to have someone watch you ride. See if they can see anything happening. Maybe they could even record it for you. If it is not actually changing gears, getting harder or easier to pedal, I'd say your initial shift isn't seating right on the cog. The jump you feel would be the chain slipping into the correct position.
Last edited by tornado60; 05-27-21 at 03:25 PM.