Whenever I'm lifting heavy (for me), I sometimes do my last rep, stand up, and get a weird feeling like the vein (or whatever it is) next to my throat, along the front side of my neck flexes hard, or tenses up? It lasts for about 10 to 15 seconds and then instantly goes away. It doesn't hurt, but it does feel very strange.
I've never felt anything like this, it's been happening the last six months maybe?

I think it mostly happens on chest and shoulders..