Do you really have to grind? Just do every map market that is medium or low challenge. As you level up more and more markers will drop to that and by the time you clear all markers you will be 40-43 and be ready to meet Takemura 
For easy respawns - Pacifica beach or Valentinos pier - but those may be bit higher level on start. For more info you can check my list: https://rk.edu.pl/en/cyberpunk-2077-gameplay-tips-and-tricks/ - note that on lower levels and no quest progression the Pacifica beach may not spawn civilians which is way better for farming them (although if you want to reach max level and not nececarily max out skills going for the 2 packs of 3 mobs on highest difficulty is better - quicker).
For easy respawns - Pacifica beach or Valentinos pier - but those may be bit higher level on start. For more info you can check my list: https://rk.edu.pl/en/cyberpunk-2077-gameplay-tips-and-tricks/ - note that on lower levels and no quest progression the Pacifica beach may not spawn civilians which is way better for farming them (although if you want to reach max level and not nececarily max out skills going for the 2 packs of 3 mobs on highest difficulty is better - quicker).
You can do gigs (minor side jobs) and reported crimes to grind xp. Gigs are yellow exclamation points on your map (though so are main missions, and vehicles you can buy. Hover over them with your mouse to make sure it's not a vehicle purchase). Crimes are the light blue symbols, there's a few different types. Most of them are short and quick (4-8 enemies), the blue skull ones are organized crime locations which are a little bigger (10-20 enemies) and can have some cool loot lying around.
If you don't like those you can find spots where there's gangoons standing around and just run through the neighbourhood killing them repeatedly. There's plenty of YT videos with good locations and routes.
If you don't like those you can find spots where there's gangoons standing around and just run through the neighbourhood killing them repeatedly. There's plenty of YT videos with good locations and routes.
Man, you can just download wemod and knock it out in a single keystroke.
Those are all late-game locations and not suitable for a low-level character.
Pacifica is ok after you leave Watson, and in Watson during night you have respawning mobs in few areas.
I would advice against level farm as you easily destroy combat. The area where you meet Mamma Welles is pretty good, bunch of spawns with level 28 Valentinos in the area. They can easily one-shot you your level, but a good sniper rifle or pistol will help you clear them out fairly fast and level both xp and street cred quickly.