Awaken with left side of tongue swollen, stuck to side of check. Affects speech. Back to normal within a few hours. Happened x3 in a couple of months?

Have exam. This sounds like a small gland (like a sweat gland) on the side of the tongue might have a clogged duct which causes the swelling which then subsides as the duct slowly allows the fluid to drain. See an oral surgeon.
See an allergist. Painless swelling that resolves within a few hours is called angioedema. It can be associated with hives, occur on its own, or can be associated with a few diseases. If you are on blood pressure medications such as lisionpril, (ace inhibitors), these are notorious for causing such symptoms. If you are not, you should see a board-certified allergist/immunologist.