Okay So My Other Half Has Been Getting Very Dizzy,

Okay so my other half has been getting very dizzy, feeling crossed eyed but isn't and his pupils get small and he basically just looses consciousness and his speech gets slurred tends to only happen at night and when he's driving or doing something sitting down. Wakes up feel dizzy. He's had many head injuries before but didn't hit his head this time. Afraid it might be something bad help