Hi all, hopefully I can get some help with this one. My car is automatic transmission 4speed/ triptronic.

Driving around town, it shifts normally. Have noticed a few times that when I'm on the highway, it gets stuck in 2nd gear, before eventually shifting into 3rd. Even releasing the throttle and applying again doesn't shift it straight away.

Would this be a throttle body issue? transmission issue?

I've only recently purchased this car too, so I don't know it's prior history. Bought from a car yard. I'm wanting to get a transmission service done but I don't want too if I need to fix the above issue first and waste my time getting the service done