It has been noticed that earthquake activity in Öræfajökull volcano is slowly increasing. At the moment this increase is just in the form of minor earthquakes taking place in the volcano at 5 – 10 km depth (at the moment). This was covered in a Icelandic news two days ago (when this is written), the volcanologist in the news (Páll Einarsson) says this is nothing to worry about at the moment, that I agree with, mostly, he also put forward that idea this process, if it evolves into an eruption might take up to 18 years from start to finish, as was the case with Eyjafjallajökull volcano. This is where I disagree with the professor Páll Einarsson, the reason being that this process already started good 10 years ago, I also suspect that Öræfajökull volcano to be a volcano that erupts suddenly and with a lot of force once it does erupt.
The eruption in the year 1362 had the VEI of 5 and the eruption in 1727 had the explosive force of VEI=4. Both eruptions lasted several months. Öræfajökull volcano only makes ash rich, explosive eruptions, based on latest historical data and studies into the volcano history. The processes that power Öræfajökull volcano might also be different, since there is an slab of old continental crust (study: Continental crust beneath southeast Iceland) under Öræfajökull volcano, that is slowly melting due the nearby hotspot. This means the magma is mostly silica, not far from the magma found in volcanoes found at subduction zones around the world.
There is also a second volcano this same area that has been showing sign of increased activity. That volcano is called Esjufjöll, it has even less understood activity (if any) since people moved to Iceland ~1300 years ago. There is a chance of an unconfirmed eruption in the year 1927, but it didn’t last long, maybe up to five days, it was mostly noted due a glacier flood from the area this volcano is located (small according to historical documents).