Why did the Norwegian forces of WW2 surrender so quickly instead of engaging the Germans in a shooting war like say Finland?

I'll try and give a quick answer because I have to go to bed so here goes

There are numerous differences between these two situations. I am going to assume you are referring to the Winter War when it comes to Finland and if so there were very many factors in the Finns favor that the Norwegians would not have had.

They're foes varied a great deal. The Soviets had just gone through a series of purges that were devastating to the officer class leaving it under-qualified with many officers chosen for political loyalty instead of merit, this along with the low morale of the average soldier, improper supply lines etc meant that the Soviet side of the conflict was more or less a complete shambles. Contrast this with the Germans at the beginning of the second world war. The Germans had developed strategies, tactics and weapons that had allowed them to steamroll over France and the low countries along with sending British forces back across the channel in only a few short months. The average German soldier would have had excellent morale along with being well supplied with the arguably the best military equipment in the world at that point and competently led by officers trained and chosen based on skill and merit.

While I am unsure of the state of the Norwegian military at that time I can tell you that the Finnish military had well-trained and motivated troops fighting in their home terrain and led by an excellent general in the form of Mannerheim and the best they could do was a diplomatic settlement that saw them make significant territorial concessions to the Soviets. I imagine that the Norwegians felt it would be better to surrender instead to of fighting a short bloody war followed by an occupation by hostile soldiers.