Can I take 150 mg trazodone with halcion (triazolam)? To help with sleep initiation and sleep onset problems are is this too sedating?

Depends. How long have you been on Halcion (triazolam) or trazodone. This determines the amount of sedation you will suffer. Halcion (triazolam) is okay for short term use, but should not be used for more than a few weeks, because it is addictive and tolerance and rebound insomnia can develop. Trazodone should be only given at dose prescribed by physician, with any increase in dose determined by the doc giving it.
Possibly. 150 mg of Trazodone is common dose. Dose of Halcion (triazolam) if high enough could be excessive. Otherwise, Halcion (triazolam) acts more quickly and does not last long. The Trazodone would be expected to keep you asleep. Waking up the next morning could be a problem.