This usually comes because your brain is believing you should be able to work on multiple things at once.
The reality is your brain is like an hourglass.
It is designed to work on one thing at a time just like an hourglass only lets one piece of the sand pass at a time.
So take a breath, let it out.
Then, approach your tasks one at a time and ONLY focus on that one task. I recommend you stop your email from pinging or constantly loading. Mine is manually loaded and I grab it at certain times of the day so I am not continually disrupted by the notion “I have to do multiple things at one time.”
This is always why prioritizing your day in the morning and setting your daily strategic time is so important- it lets your brain let go of trying to do too much at once and focus one at a time.