your thermostat may be showing it's age. i had the same symptoms after HG job, then the temp swings got more noticeble so i replaced the t'stat which made the temps a constant 90-95C. i'm running with an 83C thermostat now which makes it run a little cooler at around 85-90C.
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"