Another point is, I think, if you're new to jazz, it's very helpful to know the song. Only then you have the key to understand and find it really exciting what is improvised.
For example, even if it's a bit trite for jazz routiniers, almost everybody knows "Summertime". Miles Davis plays such a spare as brilliant solo on the old recording. Or Cannonball Adderley's solo on "Autumn leaves", again with Miles Davis. The most important thing is, if it's not a pleasure, don't force yourself. If it is joy, then it can happen without having to know much about it.
