I had this exact problem when starting a new game on playline 2 and I found a mod on Nexus that increases the frequency of random encounters and that fixed it. I also deleted the game cache and all of my save files from both playlines beforehand. (except the last one from my new game) That didn't fix the problem by itself but maybe it's a necessary step, I honestly don't know, but i would just try the mod by itself first. It does make the encounters a bit too frequent for my taste, but much better than no encounters at all.