There's evidence that some of the dinosaurs may have had endothermic features, in a primitive way, that is, not in the same way of modern mammals or birds. Birds are reptiles too, btw.
Birds are most decidedly NOT reptiles. They are of the class aves, one of the five classes of vertebrates. The other four classes are: fish, amphibians, reptiles and mammals.
There is very strong evidence that dinosaurs could not have been cold-blooded and survived. Some of the things that back up this assertion are:
*Large sauropods would never have been able to rely on external temperatures to heat their bodies because of their size, and the amount of time it would have taken them to "heat up" would have left virtually no time for any other activity.
* Predator/prey ratios among concentrations of fossilized remains indicates that the ratio was much closer to that of warm blloded predator environments. For example, consider lions vs. zebras (i.e. relatively small numbers of lions, who must consume eat frequent and consume large numbers of prey to maintain their metabolism, relative to the prey population. If the predator dinosaurs were truly cold blooded, smaller populations of prey animals would be able to support relatively large populations of predators, because reptiles don't need to consume so many calories to maintain their metabolism.
*The apparent lifestyle of the two-legged raptor-type dinosaurs required a great deal of energy to chase and kill prey. The current belief is that they were aggressive predators with a lot of stamina, as opposed to cold blooded reptiles who mostly lie in wait and are capable only of relatively short bursts of energetic activity.
I am not a paleontologist, but I have done a lot of reading on this subject, and was absolutely stunned back in the late '70s when a scientific consensue began to emerge that dinosaurs really were warm-blooded. I know there are some paleontologists who disagree with that premise, but they are relatively few in number, so I am given to understand.