Due to the pandemic, Istanbul shouldn’t be too busy at the moment, but still might be worth making arrangements beforehand.
If you are looking for central/touristy place, there are lot of hotels in the sultanahmet area near Hagia Sofia / Grand Mosque. It’s very walkable and there is also regular tram service from there to other parts of the city so easy to go places.
You can also look for a place along Istiklal street. Lot of shops, restaurants, bars as well as access to transportation but you are a bit further away from the main tourist attractions.
It’s a fascinating city to visit and spend a few days. Enjoy your trip!