late afternoon weakness

hi,
I'm experiencing something strange, almost everyday late afternoon like between 6pm and 10pm I'm having such energy drop that I feel weak legs and tightness in my face.
What can it be, anxiety? I can add that since some time I have something like heart palpitation when quickly lie down or bend over. Temporary difficulties with breathing when this happens, usually few seconds. weird. Usually I have more energy late night. Tweet