What Do Episodes Of Extreme Shaking In A Person With Multiple Myeloma Indicate?

My 77 year old father has episodes of extreme shaking due to feeling very cold even he is in a warm room. This last several hours and leaves him exhausted. He had seen a Infectious disease Dr, ran a lot of tests, nothing came of it. It s almost seems like a seizure of some sort. He is diabetic and is currently being treated for Multiple Myeloma. These seizures have been happening for several years, he just had one a few days ago, but the last one was almost a year ago. He began treatment for the Cancer a month ago. He has been a diabetic for several years. When it starts he begins to get cold , can t seem to warm up, then the shaking starts. My mother does everything to warm him up , heating pads, blankets, extra clothing. The last episode lasted nearly all night. Any help with this would be greatly appreciated.