Did any German generals warn Hitler not to get overconfident of victory over the UK and USSR in World War II?

Germany's generals tried desperately to get Hitler to listen to them, but the fool insisted on several decisions that cost them a lot of lives and losses.

Germany would have eventually lost the war anyway. They never had enough resources to sustain a war long enough to allow them to reach Hitler's goals. The best they could have hoped for is a surrendered stalemate that would allow them to rescind The Treaty of Versailles and bring Germany back from the poverty it was suffering from.

Nope. There were worries about going to war with France. But they didn’t worry about Britain as they didn’t have a sizable army to thwart Germany. Most of the generals didn’t have a problem invading Russia. By then they had so many successes they believed Hitler. They all believed the Soviets would fall. German army doctrine has historically always understood it would fight outnumbered. That’s why they believed in quality and winning decisive battles at the outset of a conflict. That said, their analysis of Soviet capabilities, potential, and current strength were ridiculously off. Their logistics folks realized the numbers of equipment and men needed and the goals and timelines didn’t add up, but the general feeling was “we’ll just figure it out when we get to that point”. 

Incidentally, Hitler also didn’t consider the US a real threat either. They didn’t have respect for the character of the American people, military capabilities, industrial might, or potential. 

A fair number of them (most notably, Hermann Goering - head of the Luftwaffe) tried to, but Hitler was too stupid and drugged up to heed their warnings.

No no no..that would have had bad results...even if everyone knew it was true besides Hitler.

if they did, he had them taken out back and "ol yellered" 

he tried to make one of his top generals commit suicide after a single loss, it was a big loss, but still just the one  

Apparently: not about overconfidence per se, but about other possible and likely consequences of the plan.

https://en.wikipedia.org/wiki/Operation_Barbarossa...

They did not dare to say anything like that.

Probably  and most likely it was near after Karl hit Hitler with a huge morning dose of meth and a sedative aka speed ball .

 Rational abounds during a rush . Three straight days non stop called Blitz . Awake and charging on speed to Poland . B17  bombers and escorts all optional speed 

Well, there was no victory against England because operation sea lion failed. Germany failed to defeat the RAF. They could not take over England without securing the sky first. As for invading the Soviet union I don't believe German generals objected. Possibly in the end when it was going bad there were objections/ talks of surrender. But initially, Germany was basically undefeated and believed they could not fail. Generals were very confident and if they were heard speaking negatively about invading the USSR it would not be taken well. 

Many of them did, but his ego just ignored them