I Am A 68 Year Old Woman, In Good General

i am a 68 year old woman, in good general health, the only medication i take is 100 mg thyroxine, today i lay down on sofa for a rest, as i dosed off, i felt my heart beat really fast, and strong, as if coming up in my throat, this lasted for maybe 3mins, then eased off, i am ok now, but i feel a bit whoosey in my head, and a slight burning in my tongue, grateful for your opinion please