EoE can have long periods of peace in the "middle game" due to how the vanilla AI works. Kingdoms will only go to war with their neighbours, and only if they have a total strength advantage. For small kingdoms such as Ireland, Scotland, etc, this means that their chances of being able to declare war are very small.

This situation will last until the "end-game" when smaller kingdoms have been swallowed up by larger ones, and the world will see much more regular conflicts between the large empires that are left.

What to do? Don't attach yourself to a single kingdom and wait for a war to happen. The renown tiers in EoE are low so that you can skip to T4 and create your own kingdom relatively quickly. One you get to this stage, you will be at constant war. Other things you can try:
attack rebels to boost renown quickly
if you are a vassal, vote for wars
only become a vassal of large, land locked kingdoms
don't become vassal, continue to merc for kingdoms already at war
fight the crusader and mujaheddin armies which are always spawning and fighting