A surprising amount of speakers of Spanish have an ř sound, usually in place of the normal trill. Specifically, it's present in New Mexican Spanish (spoken in New Mexico & Colorado), Amazonic Spanish/"Jungle Spanish" and influenced dialects (spoken in Ecuador, Peru, parts of eastern Bolivia, Paruguay, northern Chile, northern Argentinia, the Colombian highlands, and I think south Venezuela), Guatemala, and Costa Rica.

Specifically, the sound is called a voiced alveolar fricative trill. The IPA symbol is [r̝].

It's said to be due to imported influence from northern Spain (Basque Country, Navarra, La Rioja), where the same sound is also present, and varyingly from the influence of various local Native American languages, some of which in the areas have/had the sound.

In some of those dialects, a pronunciation like [ʐ] may be used instead, which I think is similar to what's spelled ż/rz in Polish. The pronunciation can weaken further into [ɹ̝], which might be hard to distinguish from the r sound of some English speakers, or even more to [ɹ] which is similar to the r sound in some English speech.