Normal behavior? Advice please

My kids asked for a pet turtle, and I, very naive and uneducated about turtles, thought it would be an easy pet.

We got a red eared slider, the woman in the aquarium store sold us a very small enclosure, and said that would be ok for a while.

Didn’t seem right to me so I investigated and got a much bigger tank, filter, basking platform, water heater, thermometer and uva/uvb light. Big river stones, a small cave and calcium blocks have been ordered too.

While in the small enclosure, the slider was quite still, and would only move when fed. We set up the bigger tank today, and put the slider in there, at first it was hanging on to the basking platform, but as the water started to warm up, it started to move a lot, seems almost desperate.

I think is because of the now appropriate temperature and space, but just to make sure I added a video and would like to read your opinions and suggestions. Thanks!