The Colorado football head coach has returned to campus after having surgeries last week ... and he was in such a good mood, he was caught on camera dancin' and groovin' to some old-school music in his office!!

Deion Sanders Jr. posted the fun footage to Primetime's social media page Tuesday afternoon ... showing the 55-year-old Buffalo head man sitting at his desk and blasting One Way's "Push."

You can tell the former Dallas Cowboys star was feeling great ... 'cause he was belting out some of the lyrics, while dancing up a storm in his chair.

It's all an amazing sight ... considering what the NFL legend had to go through just a couple days ago. You'll recall, he needed another procedure on his foot ... in addition to a surgery to remove some blood clots. The time with the doctors was so serious, it actually wiped him out of his scheduled appearance at Pac-12 Media Day.

But, Sanders Jr. wrote as a caption on the vid that everything appears to be going smoothly now.

"My dads 1st day back In the office and he was happy as can be!" Sanders Jr. said. "Even tho he's supposed to be at home resting… but he said 'I’ve got to see my Dogs.'"

"We’re about to shake up college football like never b4!"