How do you express the need to experiment a sexual desire with your partner that you feel may make them feel uncomfortable?

This depends on 1. how long your relationship is and 2. how open your partner is to the idea. For me, the best way to open it up is first, find a good timing. It can be when you are both chilling while watching your fave movie or simply just enjoying the company of each other at home. You can open the topic up slowly and lightly as possible and try to weigh your partner's reaction. Of course, if you feel that your partner is a bit uneasy, you can always try it in another time. Respect and understanding are always essential keys in bringing this kind of topic.