yep, your radio is going into oscillations.
the main reasons for this are:
1. high antenna SWR
2. mistuned transmitter
3. power supply insufficient (radio starving for current)
the first two reasons are pretty straightforward, but the last one may sound confusing if you havent run into it before.
in the most basic sense, what is happening is that your radio is putting out the 40 watts (for example) which is the max peak amperage your power supply can deliver.
however, the power supply can only deliver that amount of current for a split second, and then it drops off.
when the current drops off, but the radio hasnt been switched back to RX mode, the TX section goes crazy and start oscillating due to the flywheel effect.
turn your mic gain down until the radio is only peaking about 15 watts or so, and see if its still having the problem.
if it is, see reasons 1 and 2.
if not, reason 3 is your culprit.
LC