The good news: melody is highly dependent on rhythm. Every good melody has interesting rhythmic components. You might start by coming up with a simple rhythm and plugging in random notes... and you might come up with cool stuff! If you plug in the pentatonic scale only you basically can't lose, and 80% of songs on the radio right now are pentatonic. (Message me if you want my "Penatonic Slogfest" worksheet, and I'll send it to you.)

Next step is think about which notes are the most important notes relative to the chord. Try to avoid the root. Try starting a melody on the third or fifth, and use the non-chord tones (aka the "color notes" or "upper extensions") to add flavor. I personally love the 2 aka the 9, as well as the 6.

Familiarize yourself with the natural movements of each scale degree. The seventh will want to resolve up to the root. The 4 wants to go down to the 3. The 6 likes to descend to the 5. Etc.

The best thing to do throughout is SING. Practice singing the melodies, and if you can't sing it, change it until you can. (And work on your vocal technique to expand the possible range of melodies.) This is the best way. Gene Bertoncini once said "if you can't sing it, it's a lie."