I had chills nonstop all through March and April, likely due to stress. I literally wore 2 jackets and wrapped myself in a blanket, only to still be freezing cold (and drenched in sweat). But I have 2 rare immune-mediated neurological diseases affecting my peripheral nervous system. So, undoubtedly my immune system is messed up.
I still get chills off and on but it has been better after moving from the US to Croatia (I am a dual citizen of both countries). I think the stress of Trump (as a disabled person) and the coronavirus situation in the US really messed up my health overall and eventually caused these chills. Coronavirus pandemic did totally change my medical care situation in the US for the worst too.
I still wear a continuous temperature monitor (using a zero heat flux sensor—it’s used in critically ill patients) to help pick up on these events. The device I use was recently cleared as a medical device under emergency use authorization by the FDA in the US: https://corebodytemp.com/