@vonVile
That sums up pretty much my experience I had with Valheim early in my playing.

Everytime you are longer in your base, any "base" you have, it rolls a dice and sends a raid.
A "Base" is when three items are close enough to each other, that being a bed, campfire among others. You can read the detail on the Wiki.
One way to spit into he games soup of raids is to do what Retsam1 said so niceley:

Originally posted by retsam1:

Why do you not have your bases protected with trenches earthen walls etc etc?

Just dig a trench around stuff, deep enough so the walls of it are steep and tall enough so you can't walk out without using sprint. Either that or pile up earth walls.

The other thing you can do.... place campfires everywhere... campfires are not directly targeted by enemies, but they do prevent enemy spawn around them even when not lit up, so what I did was dot a huge area around my base with campfires.
Prevents enemies from spawning close by, even raids. This can be misused because the defensive mechanics in Valheim are half-baked.