[sametmax]

There are add ons to change the user agent to something more generic. You can even randomize it but it breaks many more sites than I was expecting.

[roblabla]

I think randomizing the UA might actually be worse, since it would allow services to fingerprint you across calls more precisely.

The point is to not ever be different from others. Act like the rest of the crowd. By changing your UA every now and then, you stand out, and become easier to identify.

[ReverseCold]

If by randomizing you mean random strings (and not from a list), then I think this is relevant:

https://xkcd.com/1105/

[sametmax]

Randomly selected from a pool of known UA.