It happens to me too

In one line:
an item placed at the side of the belt that speeds up the belt for the next let's say 5-10 tiles.

What exactly:
An item or items (size 1x1 or 2x2) placed at the side of the belt (like a rail stop or chain signal) that speeds the next x belt tiles.

Why:
You said Yourself that making ...

idea 1:
New rail type - the rails we have look kinda like a steel on wood... maybe let's introduce some new rail type ? like this: https://greens.org.au/sites/greens.org.au/files/field/image/high_speed_rail_1920x1005.jpg

idea 2:
New underground belt type - simply a LONGER version. Or maybe a ...