Unidentified Feeling – no clue how to place it

Last night when I was having one of my awake spells (tons of thoughts come at me all at once for about 1-2 hours sometimes)… I suddenly felt the feeling go through me that I was unable to identify.

My whole body got hot and then there was a pulsing sensation – almost like I got embarrassed, or felt shame, but that wasn’t it. I have no idea what caused it or why, but I know there was a lot of anxiety riding on top of it.

How do I go about identifying a feeling that doesn’t seem to have a thought that triggered it or anything that makes itself known?

I feel like maybe this is a feeling that is there all the time, but I just became aware of it last night. I’d really like to do some work on it to identify it because it somehow felt important to me, but I don’t know where to go from here.