Analog.com Tutorials
TI Training and Videos
SparkFun Learn
Adafruit Learn
Hackaday
Way more to add.
What are Microcontrollers?
What are Integrated Circuits?
PCB Basics
Analog-to-Digital Converters
What are Biopotentials
For every chip you are interested in, read the datasheets thoroughly. They are INVALUABLE resources for learning analog circuit design.
Specific youtubers to check out:
Phil's Lab
Robert Cox
ElectroBOOM
Physics Videos by Eugene Khutoryansky
Gadgetronics
Zack Freedman
3Blue1Brown