Do I need to sand and prime before painting my bed frame?

Lightly sand,clean,prime with Kilz or Zinser,allow to dry,paint and seal with a non yellowing polycrylic.

Since this is a bed, I would suggest finding a no/zero voc primer (like harmony from SW). Off gassing in a bedroom environment affects some people more than others but is quite unpleasant (and a health risk).

And yes, do sand and prime. :)

I say "yes" to sanding also. Paint won't stick to a shiny, lacquered surface, or to dirt, so a good sanding AND cleaning are important if you want a good result that lasts. Try a spray cleaner like Krud Kutter or TSP. Super easy!

https://www.woodcraft.com/products/krud-kutter-tsp-substitue-32-oz

I recently painted a four poster bed for my guest room. I just cleaned it really good and it had no rough spots so I used Plaster Paint and it has held up beautfully.