Oscar ramming glass while sleeping

Notice my oscar sometimes rams the glass hard when sleeping. He did it like 5 times this morning.
Also floats on his side when sleeping.

Is this normal? Worried he will hurt himself one day when doing this.

4 y/o Oscar in 125 gallon tank.

 

The ramming sounds kind of odd...the worst i have seen was a betta i had would "sleep swim" and randomly drop like a rock from near top of tank onto gravel. No clue how to stop it. Is it a daily thing? Or just a random notice kind of thing?

 

The ramming sounds kind of odd...the worst i have seen was a betta i had would "sleep swim" and randomly drop like a rock from near top of tank onto gravel. No clue how to stop it. Is it a daily thing? Or just a random notice kind of thing?

Random. Yesterday he did it like 5 times over the course of a few hours. Might go a month before he does it again.
Maybe he's just having bad dreams. Its not really ramming, just freaking out while sleeping and hitting glass. Then floats back upp on his side and keeps sleeping (he often/always sleeps sideways)

 

He hit glass another couple times. Now just 2 days after a 40% WC, so water must be clean.
Could it be light reflections while his tank is dark?

 

He hit glass another couple times. Now just 2 days after a 40% WC, so water must be clean.
Could it be light reflections while his tank is dark?

Possibly. I figure if he sleeping and sees something not immediately recognizable, definitely possible to react in anger, especially if groggy and confused.