Not sure about pricing for my idea (still MVP). Is it weird if I show it for free to users and then some features go premium?

Making some features go premium after it was free may create a bad vibe about your brand reputation in my opinion. So if you want to do this you have to make it clear that some features will go premium and have to state which features will go premium.

As a general rule, you should never take away from your users something which they already have. That's likely to cause resentment and mistrust.

Applying this principle to your situation means: No, Don't make something free and then take some of it away and make it premium.

Instead:

• Show which features are premium right off the bat,
• Say that the features are in beta and it hasn't been decided whether they are free or premium, or
• Convert some existing free features to premium, but keep them free for existing users (ie. grandfathering)

Or some variation/combination of the above.

If you're still in the MVP phase and looking for your first customers, I think you can offer these features for free or at a heavy discount for your first users. After all, getting your first customers and setting a foundation for your business in the long run should be your main priority at this stage. Rewarding early users with premium features or grandfathering them in at a certain price is beneficial to both you and them. They will get a great deal and also be able to give you valuable feedback about features of your MVP that you can refine and prioritize as you move forward.

Hope this helps.

If users aren't aware this might happen, I think it will turn them off.
If you offer premium features as a free trial, then I think people will understand & those who see the value will pay.