Given that the Cold War is generally accepted to have ended less than a quarter of a century ago (and recent developments have led some to suggest that certain elements of it are still with us today), historical thought on "who started it" is definitely contentious.

There are fingers that one can point on both sides as to "who started it", and they mostly emerged at the Potsdam Conference of 1945. President Truman was a hardline anti-communist, and ended measures of co-operation (including lendlease) that had been established between Roosevelt and Stalin throughout negotiations during WWII. Stalin decided to exclude democrats (who were hiding in London in exile) from the new Polish government, reneging on a previous agreement to do so. The sharp decline in their relations proceeded from a position of mistrust from that point onwards; the Soviets began developing nuclear weapons to create a perception of parity in arms, and the US furthered their policy of containment to keep communism out of Western Europe. At the time that the Cold War is generally thought to have started, both sides were unhappy with their position in relation to each other and both sides had an equal stake in the competition between them.

There are moments that suggest during the Cold War that elements in both sides were certainly unwilling to be in the conflict and did their utmost to cool off relations (if you'll pardon the pun). Nikita Khrushchev's measures of goodwill around the Kennedy inauguration, as well as Nixon's strong advocation of détente, imply that there were individuals both sides who acknowledged the ideological differences between both powers but were, even at least temporarily, more interested in fostering economic relations and disarmament than an advancement of the war footing.

I think what you are looking for is the historiography of the cold war.

The Three (ok Four) prominent schools of thought on the Cold War:

1. The First generation/Orthodox: this school of thought was prominent in the 50s, which essentially agreed with the official American position that the cold war was started by Soviet expansion into Eastern Europe and the ideology of international Communism.

2. The Revisionist: prominent in the Vietnam/Post-Vietnam era, this school of thought looks at pre-1945 US/USSR relations and formulates that Soviet leaders essentially took eastern Europe as a defensive measure, and that the cold war was the continuation of older US-Russian rivalry. It sees the US as a hegemonic seeking force which wanted to contain the Soviet Union as a challenge to its national power.

3. Post-Revisionism: this School rejects some of the key claims of the revisionists while accepting others. In essence it proposes that: "neither side can bear sole responsibility for the onset of the Cold War." they put forwarding the argument that conflict between the US and USSR was to some extent inevitable and both sides are responsible for it.

4. Post-Cold War: With the end of the cold war and the opening of Soviet archives, nowadays historians focus a lot less on blaming one side or the other and a lot more on the structure of the cold war.

This was a topic of some discussion in one of my more advanced political science classes in college (BA in poli sci). I agree with the varied schools of thought mentioned elsewhere, and the most recent thinking on the subject is somewhat grounded in game theory and the concepts of incomplete information.

Basically, at the close of WWII, the USSR occupied much of Eastern Europe, while the western allies were in control of the western half. Each party maintained large numbers of soldiers, by virtue of both 1) having just concluded a major conflict, and 2) neither side really trusted the other. The West was concerned with Soviet expansionism (ie the installation of communist puppet regimes in most of the countries they occupied), while the USSR was concerned due to the massively destructive war they had just finished and the (at that point) American monopoly on nuclear weapons.

Each side had legitimate concerns about the other that gave rise to an atmosphere of mistrust and competition. They could each say to the other "we're solely concerned with self-defense and not a threat to you", but talk is cheap. They would have had to undertake a major action in order to prove they meant what they said. Something drastic like withdrawing all troops from the occupied zones.

Neither side was prepared to do something like that, so lacking complete information on everyone's intentions, each power bloc was forced to act based on what they did know and assume the worst so their defense would not be compromised. Hence, intense competition and mistrust leading to the Cold War.